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Sample records for singlet oxygen concentration

  1. Singlet oxygen quenching by oxygen in tetraphenyl-porphyrin solutions

    International Nuclear Information System (INIS)

    Dedic, Roman; Korinek, Miloslav; Molnar, Alexander; Svoboda, Antonin; Hala, Jan

    2006-01-01

    Time-resolved measurement of singlet oxygen infrared phosphorescence is a powerful tool for determination of quantum yields and kinetics of its photosensitization. This technique was employed to investigate in detail the previously observed effect of singlet oxygen quenching by oxygen. The question whether the singlet oxygen is quenched by oxygen in ground or in excited state was addressed by study of two complementary dependencies of singlet oxygen lifetimes: on dissolved oxygen concentration and on excitation intensity. Oxygen concentration dependence study of meso-tetra(4-sulphonato)phenylporphyrin (TPPS 4 ) phosphorescence kinetics showed linearity of the dependence of TPPS 4 triplet state rate-constant. Corresponding bimolecular quenching constant of (1.5±0.1)x10 9 l/mol s was obtained. On the other hand, rate constants of singlet oxygen depopulation exhibit nonlinear dependence on oxygen concentration. Comparison of zero oxygen concentration-extrapolated value of singlet oxygen lifetime of (6.5±0.4) μs to (3.7±0.1) μs observed under air-saturated conditions indicates importance of the effect of quenching of singlet oxygen by oxygen. Upward-sloping dependencies of singlet oxygen depopulation rate-constant on excitation intensity evidence that singlet oxygen is predominantly quenched by oxygen in excited singlet state

  2. Glow discharge in singlet oxygen

    International Nuclear Information System (INIS)

    Vagin, N.P.; Ionin, A.A.; Klimachev, Yu.M.; Sinitsyn, D.V.; Yuryshev, N.N.; Kochetov, I.V.; Napartovich, A.P.

    2003-01-01

    Currently, there is no experimental data on the plasma balance in gas mixtures with a high content of singlet delta oxygen O 2 ( 1 Δ g ). These data can be obtained by studying the parameters of an electric discharge in singlet oxygen produced by a chemical generator. The O 2 ( 1 Δ g ) molecules significantly change the kinetics of electrons and negative ions in plasma. Hence, the discharge conditions at low and high O 2 ( 1 Δ g ) concentrations are very different. Here, the parameters of the positive column of a glow discharge in a gas flow from a chemical singlet-oxygen generator are studied. It is experimentally shown that, at an O 2 ( 1 Δ g ) concentration of 50% and at pressures of 1.5 and 2 torr, the electric field required to sustain the discharge is considerably lower than in the case when all of the oxygen molecules are in the ground state. A theoretical model of the glow discharge is proposed whose predictions are in good agreement with the experimental data

  3. Singlet Oxygen at the Laundromat

    Science.gov (United States)

    Keeports, David

    1995-09-01

    Singlet molecular oxygen is an interesting molecule both visually and theoretically, since its red chemiluminescence can be analyzed by the application of simple molecular orbital theory. It can be produced from the reaction of hydrogen peroxide from either chlorine gas or hypochlorite ion from household bleach. Here we demostrate how to produce it using simple laundry cleansers.

  4. Advanced Singlet Oxygen Generator for a COIL

    National Research Council Canada - National Science Library

    Kodymova, Jarmila; Zagidullin, M; Nikolaev, V; Svistun, M; Khvatov, N; Hruby, J; Spalek, O; Jirasek, V; Censsky, M

    2005-01-01

    This report results from a contract tasking Academy of Sciences as follows: The Grantee will develop new and radically different ideas for a high performance, advanced singlet oxygen generator for driving a supersonic COIL...

  5. Singlet oxygen-mediated damage to proteins and its consequences

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan

    2003-01-01

    by the transfer of energy to ground state (triplet) molecular oxygen by either protein-bound, or other, chromophores. Singlet oxygen can also be generated by a range of other enzymatic and non-enzymatic reactions including processes mediated by heme proteins, lipoxygenases, and activated leukocytes, as well...... the absorption of UV radiation by the protein, or bound chromophore groups, thereby generating excited states (singlet or triplets) or radicals via photo-ionisation. The second major process involves indirect oxidation of the protein via the formation and subsequent reactions of singlet oxygen generated...... as radical termination reactions. This paper reviews the data available on singlet oxygen-mediated protein oxidation and concentrates primarily on the mechanisms by which this excited state species brings about changes to both the side-chains and backbone of amino acids, peptides, and proteins. Recent work...

  6. Holographic monitoring of spatial distributions of singlet oxygen in water

    Science.gov (United States)

    Belashov, A. V.; Bel'tyukova, D. M.; Vasyutinskii, O. S.; Petrov, N. V.; Semenova, I. V.; Chupov, A. S.

    2014-12-01

    A method for monitoring spatial distributions of singlet oxygen in biological media has been developed. Singlet oxygen was generated using Radachlorin® photosensitizer, while thermal disturbances caused by nonradiative deactivation of singlet oxygen were detected by the holographic interferometry technique. Processing of interferograms yields temperature maps that characterize the deactivation process and show the distribution of singlet oxygen species.

  7. Single Cell Responses to Spatially Controlled Photosensitized Production of Extracellular Singlet Oxygen

    DEFF Research Database (Denmark)

    Pedersen, Brian Wett; Sinks, Louise E.; Breitenbach, Thomas

    2011-01-01

    The response of individual HeLa cells to extracellularly produced singlet oxygen was examined. The spatial domain of singlet oxygen production was controlled using the combination of a membrane-impermeable Pd porphyrin-dendrimer, which served as a photosensitizer, and a focused laser, which served...... to localize the sensitized production of singlet oxygen. Cells in close proximity to the domain of singlet oxygen production showed morphological changes commonly associated with necrotic cell death. The elapsed post-irradiation “waiting period” before necrosis became apparent depended on (a) the distance...... between the cell membrane and the domain irradiated, (b) the incident laser fluence and, as such, the initial concentration of singlet oxygen produced, and (c) the lifetime of singlet oxygen. The data imply that singlet oxygen plays a key role in this process of light-induced cell death. The approach...

  8. Singlet oxygen production and quenching mechanisms in travelling microwave discharges

    International Nuclear Information System (INIS)

    Savin, Yu V; Goryachev, L V; Adamenkov, Yu A; Rakhimova, T V; Mankelevich, Yu A; Popov, N A; Adamenkov, A A; Egorov, V V; Ilyin, S P; Kolobyanin, Yu V; Kudryashov, E A; Rogozhnikov, G S; Vyskubenko, B A

    2004-01-01

    Experimental and theoretical studies of singlet oxygen excitation in travelling microwave (TMW) discharges are presented. Singlet oxygen O 2 (a 1 Δ g ) concentrations and atomic oxygen mole fraction have been measured for different pressures, input powers and distances from the MW resonator. It was shown that a steady-state TMW discharge with a coaxial cavity resonator could provide a maximal O 2 (a 1 Δ g ) yield of 22% for 2 Torr of pure oxygen and 27-30% for He : O 2 = 1 : 1 mixture. The two-dimensional (r, z) model developed for calculations of plasma-chemical kinetics, heat and mass transfer was used for simulation of processes in the TMW discharge under study. Effects of gas pressure, gas flow rate and input power are studied and compared with experimental measurements of O 2 (a 1 Δ g ) concentrations and atomic oxygen mole fractions

  9. In-vivo singlet oxygen threshold doses for PDT.

    Science.gov (United States)

    Zhu, Timothy C; Kim, Michele M; Liang, Xing; Finlay, Jarod C; Busch, Theresa M

    2015-02-01

    Dosimetry of singlet oxygen ( 1 O 2 ) is of particular interest because it is the major cytotoxic agent causing biological effects for type-II photosensitizers during photodynamic therapy (PDT). An in-vivo model to determine the singlet oxygen threshold dose, [ 1 O 2 ] rx,sh , for PDT was developed. An in-vivo radiation-induced fibrosarcoma (RIF) tumor mouse model was used to correlate the radius of necrosis to the calculation based on explicit PDT dosimetry of light fluence distribution, tissue optical properties, and photosensitizer concentrations. Inputs to the model include five photosensitizer-specific photochemical parameters along with [ 1 O 2 ] rx,sh . Photosensitizer-specific model parameters were determined for benzoporphyrin derivative monoacid ring A (BPD) and compared with two other type-II photosensitizers, Photofrin ® and m-tetrahydroxyphenylchlorin (mTHPC) from the literature. The mean values (standard deviation) of the in-vivo [ 1 O 2 ] rx,sh are approximately 0.56 (0.26) and 0.72 (0.21) mM (or 3.6×10 7 and 4.6×10 7 singlet oxygen per cell to reduce the cell survival to 1/e) for Photofrin ® and BPD, respectively, assuming that the fraction of generated singlet oxygen that interacts with the cell is 1. While the values for the photochemical parameters (ξ, σ, g , β) used for BPD were preliminary and may need further refinement, there is reasonable confidence for the values of the singlet oxygen threshold doses. In comparison, the [ 1 O 2 ] rx,sh value derived from in-vivo mouse study was reported to be 0.4 mM for mTHPC-PDT. However, the singlet oxygen required per cell is reported to be 9×10 8 per cell per 1/ e fractional kill in an in-vitro mTHPC-PDT study on a rat prostate cancer cell line (MLL cells) and is reported to be 7.9 mM for a multicell in-vitro EMT6/Ro spheroid model for mTHPC-PDT. A theoretical analysis is provided to relate the number of in-vitro singlet oxygen required per cell to reach cell killing of 1/ e to in-vivo singlet

  10. Singlet oxygen treatment of tumor cells triggers extracellular singlet oxygen generation, catalase inactivation and reactivation of intercellular apoptosis-inducing signaling☆

    Science.gov (United States)

    Riethmüller, Michaela; Burger, Nils; Bauer, Georg

    2015-01-01

    Intracellular singlet oxygen generation in photofrin-loaded cells caused cell death without discrimination between nonmalignant and malignant cells. In contrast, extracellular singlet oxygen generation caused apoptosis induction selectively in tumor cells through singlet oxygen-mediated inactivation of tumor cell protective catalase and subsequent reactivation of intercellular ROS-mediated apoptosis signaling through the HOCl and the NO/peroxynitrite signaling pathway. Singlet oxygen generation by extracellular photofrin alone was, however, not sufficient for optimal direct inactivation of catalase, but needed to trigger the generation of cell-derived extracellular singlet oxygen through the interaction between H2O2 and peroxynitrite. Thereby, formation of peroxynitrous acid, generation of hydroxyl radicals and formation of perhydroxyl radicals (HO2.) through hydroxyl radical/H2O2 interaction seemed to be required as intermediate steps. This amplificatory mechanism led to the formation of singlet oxygen at a sufficiently high concentration for optimal inactivation of membrane-associated catalase. At low initial concentrations of singlet oxygen, an additional amplification step needed to be activated. It depended on singlet oxygen-dependent activation of the FAS receptor and caspase-8, followed by caspase-8-mediated enhancement of NOX activity. The biochemical mechanisms described here might be considered as promising principle for the development of novel approaches in tumor therapy that specifically direct membrane-associated catalase of tumor cells and thus utilize tumor cell-specific apoptosis-inducing ROS signaling. PMID:26225731

  11. Singlet oxygen treatment of tumor cells triggers extracellular singlet oxygen generation, catalase inactivation and reactivation of intercellular apoptosis-inducing signaling.

    Science.gov (United States)

    Riethmüller, Michaela; Burger, Nils; Bauer, Georg

    2015-12-01

    Intracellular singlet oxygen generation in photofrin-loaded cells caused cell death without discrimination between nonmalignant and malignant cells. In contrast, extracellular singlet oxygen generation caused apoptosis induction selectively in tumor cells through singlet oxygen-mediated inactivation of tumor cell protective catalase and subsequent reactivation of intercellular ROS-mediated apoptosis signaling through the HOCl and the NO/peroxynitrite signaling pathway. Singlet oxygen generation by extracellular photofrin alone was, however, not sufficient for optimal direct inactivation of catalase, but needed to trigger the generation of cell-derived extracellular singlet oxygen through the interaction between H2O2 and peroxynitrite. Thereby, formation of peroxynitrous acid, generation of hydroxyl radicals and formation of perhydroxyl radicals (HO2(.)) through hydroxyl radical/H2O2 interaction seemed to be required as intermediate steps. This amplificatory mechanism led to the formation of singlet oxygen at a sufficiently high concentration for optimal inactivation of membrane-associated catalase. At low initial concentrations of singlet oxygen, an additional amplification step needed to be activated. It depended on singlet oxygen-dependent activation of the FAS receptor and caspase-8, followed by caspase-8-mediated enhancement of NOX activity. The biochemical mechanisms described here might be considered as promising principle for the development of novel approaches in tumor therapy that specifically direct membrane-associated catalase of tumor cells and thus utilize tumor cell-specific apoptosis-inducing ROS signaling. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  12. High-power generator of singlet oxygen

    Czech Academy of Sciences Publication Activity Database

    Jirásek, Vít; Čenský, Miroslav; Špalek, Otomar; Kodymová, Jarmila

    2013-01-01

    Roč. 36, č. 10 (2013), s. 1755-1763 ISSN 0930-7516 Grant - others:Laser Science and Technology Centre(IN) LASTEC/FE/RKT/54/10-11 Institutional research plan: CEZ:AV0Z10100523 Keywords : high-pressure singlet oxygen generator * spray generator * centrifugal separation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.175, year: 2013

  13. Molecular and Cell Mechanisms of Singlet Oxygen Effect on Biosystems

    OpenAIRE

    Martusevich А.А.; Peretyagin S.P.; Martusevich А.К.

    2012-01-01

    There has been considered a poorly studied form of activated oxygensinglet oxygen. Its physicochemical properties (electron configuration of a molecule, reactive capacity, features) are analyzed, and enzymic and nonenzymic ways of singlet oxygen generation in body are specified. There are shown in detail biological effects of the compound as a regulator of cell activity including that determining the mechanism of apoptosis initiation. The relation of singlet oxygen and photodynamic effect ...

  14. In-vitro singlet oxygen threshold dose at PDT with Radachlorin photosensitizer

    Science.gov (United States)

    Klimenko, V. V.; Shmakov, S. V.; Kaydanov, N. E.; Knyazev, N. A.; Kazakov, N. V.; Rusanov, A. A.; Bogdanov, A. A.; Dubina, M. V.

    2017-07-01

    In this present study we investigate the Radachlorin photosensitizer accumulation in K562 cells and Hela cells and determined the cell viability after PDT. Using the macroscopic singlet oxygen modeling and cellular photosensitizer concentration the singlet oxygen threshold doses for K562 cells and Hela cells were calculated.

  15. The development of efficient two-photon singlet oxygen sensitizers

    DEFF Research Database (Denmark)

    Nielsen, Christian Benedikt

    The development of efficient two-photon singlet oxygen sensitizers is addressed focusing on organic synthesis. Photophysical measurements were carried out on new lipophilic molecules, where two-photon absorption cross sections and singlet oxygen quantumyields were measured. Design principles...... for making efficient two-photon singlet oxygen sensitizers were then constructed from these results. Charge-transfer in the excited state of the prepared molecules was shown to play a pivotal role in the generationof singlet oxygen. This was established through studies of substituent effects on both...... the singlet oxygen yield and the two-photon absorption cross section, where it was revealed that a careful balancing of the amount of charge transfer present in theexcited state of the sensitizer is necessary to obtain both a high singlet oxygen quantum yield and a high two-photon cross section. An increasing...

  16. Singlet oxygen in the low-temperature plasma of an electron-beam-sustained discharge

    International Nuclear Information System (INIS)

    Vagin, N. P.; Ionin, A. A.; Klimachev, Yu. M.; Kotkov, A. A.; Kochetov, I. V.; Napartovich, A. P.; Podmar'kov, Yu. P.; Rulev, O. A.; Seleznev, L. V.; Sinitsyn, D. V.; Frolov, M. P.; Yuryshev, N. N.

    2006-01-01

    Results are presented from experimental and theoretical studies of the production of singlet delta oxygen in a pulsed electron-beam-sustained discharge ignited in a large (∼18-1) volume at a total gas mixture pressure of up to 210 Torr. The measured yield of singlet oxygen reaches 10.5%. It is found that varying the reduced electric field from ∼2 to ∼11 kV/(cm atm) slightly affects singlet oxygen production. It is shown experimentally that an increase in the gas mixture pressure or the specific input energy reduces the duration of singlet oxygen luminescence. The calculated time evolution of the singlet oxygen concentration is compared with experimental results

  17. Measuring a 10,000-fold enhancement of singlet molecular oxygen (1O2*) concentration on illuminated ice relative to the corresponding liquid solution

    Science.gov (United States)

    Bower, Jonathan P.; Anastasio, Cort

    2013-08-01

    Much attention has focused on the highly reactive hydroxyl radical in the oxidation of trace organic compounds on snow and ice (and subsequent release of volatile organics to the atmospheric boundary layer) but other oxidants are likely also important in this processing. Here we examine the ice chemistry of singlet molecular oxygen (1O2*), which can be significant in atmospheric water drops but has not been examined in ice or snow. To examine 1O2* on ice we illuminate laboratory ices containing Rose Bengal (RB) as the source of 1O2*, furfuryl alcohol (FFA) as the probe, and Na2SO4 to control the total solute concentration. We find that the 1O2*-mediated loss of FFA (and, thus, the 1O2* concentration) is up to 11,000 times greater on ice than in the equivalent liquid sample at the same photon flux. We attribute this large increase in the 1O2* steady-state concentration to the freeze-concentration of solutes into liquid-like regions (LLRs) in/on ice: compared to the initial solution, in the LLRs of ice the sources for 1O2* are highly concentrated, while the concentration of the dominant sink for 1O2* (i.e., water) remains largely unchanged. Similar to results expected in liquid solution, rates of FFA loss in ice depend on both the initial sensitizer concentration and temperature, providing evidence that these reactions occur in LLRs. However, we find that the enhancement in 1O2* concentrations on ice does not follow predictions from freezing-point depression, likely because experiments were conducted below the eutectic temperature for sodium sulfate, where all of the salt should have precipitated. We also explore a method for separating 1O2* and rad OH contributions to FFA oxidation in laboratory ices and show its application to two natural snow samples. We find that 1O2* concentrations in these snows are approximately 100 times higher than observed in polluted, mid-latitude fog waters, showing that the enhancement of 1O2* on ice is environmentally relevant and that

  18. Singlet oxygen-mediated protein oxidation

    DEFF Research Database (Denmark)

    Wright, Adam; Bubb, William A; Hawkins, Clare Louise

    2002-01-01

    Singlet oxygen (1O2) is generated by a number of enzymes as well as by UV or visible light in the presence of a sensitizer and has been proposed as a damaging agent in a number of pathologies including cataract, sunburn, and skin cancers. Proteins, and Cys, Met, Trp, Tyr and His side chains...... in particular, are major targets for 1O2 as a result of their abundance and high rate constants for reaction. In this study it is shown that long-lived peroxides are formed on free Tyr, Tyr residues in peptides and proteins, and model compounds on exposure to 1O2 generated by both photochemical and chemical....... These studies demonstrate that long-lived Tyr-derived peroxides are formed on proteins exposed to 1O2 and that these may promote damage to other targets via further radical generation....

  19. Phenomenological model of photoluminescence degradation and photoinduced defect formation in silicon nanocrystal ensembles under singlet oxygen generation

    Energy Technology Data Exchange (ETDEWEB)

    Gongalsky, Maxim B., E-mail: mgongalsky@gmail.com; Timoshenko, Victor Yu. [Faculty of Physics, Moscow State M.V. Lomonosov University, 119991 Moscow (Russian Federation)

    2014-12-28

    We propose a phenomenological model to explain photoluminescence degradation of silicon nanocrystals under singlet oxygen generation in gaseous and liquid systems. The model considers coupled rate equations, which take into account the exciton radiative recombination in silicon nanocrystals, photosensitization of singlet oxygen generation, defect formation on the surface of silicon nanocrystals as well as quenching processes for both excitons and singlet oxygen molecules. The model describes well the experimentally observed power law dependences of the photoluminescence intensity, singlet oxygen concentration, and lifetime versus photoexcitation time. The defect concentration in silicon nanocrystals increases by power law with a fractional exponent, which depends on the singlet oxygen concentration and ambient conditions. The obtained results are discussed in a view of optimization of the photosensitized singlet oxygen generation for biomedical applications.

  20. Optical detection of singlet oxygen from single cells

    DEFF Research Database (Denmark)

    Snyder, John; Skovsen, Esben; Lambert, John D. C.

    2006-01-01

    The lowest excited electronic state of molecular oxygen, singlet molecular oxygen, O2(a 1g), is a reactive species involved in many chemical and biological processes. To better understand the roles played by singlet oxygen in biological systems, particularly at the sub-cellular level, optical tools...... including across the cell membrane into the extracellular environment. On one hand, these results demonstrate that the behavior of singlet oxygen in an intact cell can be significantly different from that inferred from model bulk studies. More generally, these results provide a new perspective...

  1. Kinetics of oxygen species in an electrically driven singlet oxygen generator

    Science.gov (United States)

    Azyazov, V. N.; Torbin, A. P.; Pershin, A. A.; Mikheyev, P. A.; Heaven, M. C.

    2015-12-01

    The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O3(υ) formed in O + O2 recombination is thought to be a significant agent in the deactivation of singlet oxygen O2(a1Δ), oxygen atom removal and ozone formation. It is shown that the process O3(υ ⩾ 2) + O2(a1Δ) → 2O2 + O is the main O2(a1Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O2(a1Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data.

  2. Pallidol, a resveratrol dimer from red wine, is a selective singlet oxygen quencher

    International Nuclear Information System (INIS)

    He Shan; Jiang Liyan; Wu Bin; Pan Yuanjiang; Sun Cuirong

    2009-01-01

    Pallidol is a naturally occurring resveratrol dimer from red wine with antioxidant and antifungal activities. In this report, with the use of the EPR spin-trapping technique, the scavenging and quenching effects of pallidol on reactive oxygen species (ROS) were investigated. The results demonstrated that pallidol showed strong quenching effects on singlet oxygen at very low concentrations, but it was ineffective to scavenge hydroxyl radicals or superoxide anions. Further kinetic study revealed that the reaction of pallidol with singlet oxygen had an extremely high rate constant (k a = 1.71 x 10 10 ). Therefore, pallidol is a potent and selective singlet oxygen quencher in aqueous systems. It may be used in singlet oxygen-mediated diseases as a pharmacological agent, which may contribute to the health beneficial effects of red wine.

  3. Singlet oxygen: photosensitized generation, detection and reaction with organic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Barik, Atanu; Indira Priyadarsini, K; Mohan, Hari; Bajaj, P N; Sapre, A V; Mittal, J P; Mukherjee, T [Radiation and Photochemistry Div., Bhabha Atomic Research Centre, Mumbai (India)

    2006-10-15

    Singlet molecular oxygen ({sup 1}O{sub 2}) is an excited state of molecular oxygen, having antiparallel spin in the same {pi} antibonding orbital. The study of singlet oxygen production and reactivity has emerged as a rich and diverse area, with implication in diverse fields, such as synthetic chemistry, polymer chemistry, photodynamic therapy, etc. There are several known methods to produce singlet oxygen, and also various techniques employed to detect it. Out of these, photosensitization method is the most popular one. In this article, photosensitized production of singlet oxygen from triplet oxygen and photosensitizers in presence of light, and its detection by the infrared luminescence at 1270 nm have been presented. Further, some results using different types of photosensitizers, effect of solvent on singlet oxygen quantum yields and lifetime have been discussed. The quenching rate constants of singlet oxygen have been determined with different types of organic molecules such as derivatives of thiourea and its analogues, hydroxy indoles and antioxidants and the results have been presented. (author)

  4. Singlet oxygen: photosensitized generation, detection and reaction with organic molecules

    International Nuclear Information System (INIS)

    Barik, Atanu; Indira Priyadarsini, K.; Hari Mohan; Bajaj, P.N.; Sapre, A.V.; Mittal, J.P.; Mukherjee, T.

    2006-10-01

    Singlet molecular oxygen ( 1 O 2 ) is an excited state of molecular oxygen, having antiparallel spin in the same π antibonding orbital. The study of singlet oxygen production and reactivity has emerged as a rich and diverse area, with implication in diverse fields, such as synthetic chemistry, polymer chemistry, photodynamic therapy, etc. There are several known methods to produce singlet oxygen, and also various techniques employed to detect it. Out of these, photosensitization method is the most popular one. In this article, photosensitized production of singlet oxygen from triplet oxygen and photosensitizers in presence of light, and its detection by the infrared luminescence at 1270 nm have been presented. Further, some results using different types of photosensitizers, effect of solvent on singlet oxygen quantum yields and lifetime have been discussed. The quenching rate constants of singlet oxygen have been determined with different types of organic molecules such as derivatives of thiourea and its analogues, hydroxy indoles and antioxidants and the results have been presented. (author)

  5. Singlet oxygen-mediated formation of protein peroxides within cells

    International Nuclear Information System (INIS)

    Wright, A.; Policarpio, V.

    2003-01-01

    Full text: Singlet oxygen is generated by a number of cellular, enzymatic and chemical reactions as well as by exposure to UV, or visible light in the presence of a sensitizer; as a consequence this oxidant has been proposed as a damaging agent in a number of pathologies including photo-aging and skin cancer. Proteins are major targets for singlet oxygen as a result of their abundance and high rate constants for reaction. In this study it is shown that illumination of viable, sensitizer-loaded, THP-1 (human monocyte-like) cells with visible light gives rise to intra-cellular protein-derived peroxides. The peroxide yield increases with illumination time, requires the presence of the sensitizer, is enhanced in D 2 O, and decreased by azide; these data are consistent with the mediation of singlet oxygen. The concentration of peroxides detected, which is not affected by glucose or ascorbate loading of the cells, corresponds to ca. 1.5 nmoles peroxide per 10 6 cells using rose bengal as sensitizer, or 10 nmoles per mg cell protein and account for up to ca. 15% of the O 2 consumed by the cells. Similar peroxides have been detected on isolated cellular proteins exposed to light in the presence of rose bengal and oxygen. After cessation of illumination, the cellular protein peroxide levels decreases with t 1/2 ca. 4 hrs at 37 deg C, and this is associated with increased cell lysis. Decomposition of protein peroxides formed within cells, or on isolated cellular proteins, by metal ions, gives rise to radicals as detected by EPR spin trapping. These protein peroxides, and radicals derived from them, can inactivate key cellular enzymes (including caspases, GAPDH and glutathione reductase) and induce DNA base oxidation, strand breaks and DNA-protein cross-links. These studies demonstrate that exposure of intact cells to visible light in the presence of a sensitizer gives rise to novel long-lived, but reactive, intra-cellular protein peroxides via singlet oxygen

  6. Singlet-oxygen therapy. Scientific and methodological materials

    OpenAIRE

    Chukhraiev, N.; Chukhraieva, E.; Gun'ko, M.; Kurik, L.; Lomeiko, S.; Marushko, Y.; Samosyuk, N.; Tkalina, A.; Vladimirov, A.; Unichenko, A.; Zavorotnaya, R.; Zukow, W.

    2018-01-01

    Radomska Szkoła Wyższa w Radomiu MEDICAL INNOVATIVE TECHNOLOGIES SINGLET-OXYGEN THERAPY Scientific and methodological materials 2018 This edition had extended and translated from ukrainian Edited by Chukhraiev N., Vladimirov A., Zukow W. Radom, Kyiv Radomska Szkoła Wyższa w Radomiu MEDICAL INNOVATIVE TECHNOLOGIES SINGLET-OXYGEN THERAPY Scientific and methodological materials 2018 This edition had extended and translated from ukrainian Edited by ...

  7. Detection of Singlet Oxygen Formation inside Photoactive Biohybrid Composite Material

    Directory of Open Access Journals (Sweden)

    Kata Hajdu

    2017-12-01

    Full Text Available Photosynthetic reaction center proteins (RCs are the most efficient light energy converter systems in nature. The first steps of the primary charge separation in photosynthesis take place in these proteins. Due to their unique properties, combining RCs with nano-structures promising applications can be predicted in optoelectronic systems. In the present work RCs purified from Rhodobacter sphaeroides purple bacteria were immobilized on multiwalled carbon nanotubes (CNTs. Carboxyl—and amine-functionalised CNTs were used, so different binding procedures, physical sorption and chemical sorption as well, could be applied as immobilization techniques. Light-induced singlet oxygen production was measured in the prepared photoactive biocomposites in water-based suspension by histidine mediated chemical trapping. Carbon nanotubes were applied under different conditions in order to understand their role in the equilibration of singlet oxygen concentration in the suspension. CNTs acted as effective quenchers of 1O2 either by physical (resonance energy transfer or by chemical (oxidation reaction and their efficiency showed dependence on the diffusion distance of 1O2.

  8. Kinetics of oxygen species in an electrically driven singlet oxygen generator

    International Nuclear Information System (INIS)

    Azyazov, V.N.; Torbin, A.P.; Pershin, A.A.; Mikheyev, P.A.; Heaven, M.C.

    2015-01-01

    Highlights: • Vibrational excitation of O_3 increases the rate constant for O_3 + O_2(a) → 2O_2(X) + O. • Vibrationally excited O_3 is produced by the O + O_2(X) + M → O_3 + M reaction. • Ozone concentrations are impacted by the reactions of vibrationally excited O_3. • Relevant to ozone concentrations in oxygen discharges and the upper atmosphere. - Abstract: The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O_3(υ) formed in O + O_2 recombination is thought to be a significant agent in the deactivation of singlet oxygen O_2(a"1Δ), oxygen atom removal and ozone formation. It is shown that the process O_3(υ ⩾ 2) + O_2(a"1Δ) → 2O_2 + O is the main O_2(a"1Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O_2(a"1Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data.

  9. Singlet Oxygen and Free Radical Reactions of Retinoids and Carotenoids—A Review

    Science.gov (United States)

    Truscott, T. George

    2018-01-01

    We report on studies of reactions of singlet oxygen with carotenoids and retinoids and a range of free radical studies on carotenoids and retinoids with emphasis on recent work, dietary carotenoids and the role of oxygen in biological processes. Many previous reviews are cited and updated together with new data not previously reviewed. The review does not deal with computational studies but the emphasis is on laboratory-based results. We contrast the ease of study of both singlet oxygen and polyene radical cations compared to neutral radicals. Of particular interest is the switch from anti- to pro-oxidant behavior of a carotenoid with change of oxygen concentration: results for lycopene in a cellular model system show total protection of the human cells studied at zero oxygen concentration, but zero protection at 100% oxygen concentration. PMID:29301252

  10. Singlet oxygen reactions with flavonoids. A theoretical-experimental study.

    Science.gov (United States)

    Morales, Javier; Günther, Germán; Zanocco, Antonio L; Lemp, Else

    2012-01-01

    Detection of singlet oxygen emission, λ(max) = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T), and the reactive reaction rate constant, k(r), for the reaction between singlet oxygen and several flavonoids. Values of k(T) determined in deuterated water, ranging from 2.4×10(7) M(-1) s(-1) to 13.4×10(7) M(-1) s(-1), for rutin and morin, respectively, and the values measured for k(r), ranging from 2.8×10(5) M(-1) s(-1) to 65.7×10(5) M(-1) s(-1) for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

  11. Singlet oxygenation in microemulsion catalysed by vanadium chloroperoxidase

    NARCIS (Netherlands)

    Renirie, R.; Pierlot, C.; Wever, R.; Aubry, J.-M.

    2009-01-01

    Non-ionic microemulsions compatible with the enzyme vanadium chloroperoxidase were designed to perform singlet oxygenation of apolar substrates. The media were based on mono- and polydisperse ethoxylated fatty alcohols (CiEj). octane and aqueous buffer. "Fish" diagrams were determined to identify

  12. Label-free electrochemical detection of singlet oxygen protein damage

    Czech Academy of Sciences Publication Activity Database

    Vargová, Veronika; Gimenez, R.E.; Černocká, Hana; Trujillo, D.C.; Tulli, F.; Zanini, V.I.P.; Paleček, Emil; Borsarelli, C.D.; Ostatná, Veronika

    2016-01-01

    Roč. 187, JAN 2016 (2016), s. 662-669 ISSN 0013-4686 R&D Projects: GA ČR GA13-00956S Institutional support: RVO:68081707 Keywords : singlet oxygen protein damage * surface-attached protein stability * mercury and carbon electrodes Subject RIV: BO - Biophysics Impact factor: 4.798, year: 2016

  13. Singlet Oxygen Reactions with Flavonoids. A Theoretical – Experimental Study

    Science.gov (United States)

    Morales, Javier; Günther, Germán; Zanocco, Antonio L.; Lemp, Else

    2012-01-01

    Detection of singlet oxygen emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, kT, and the reactive reaction rate constant, kr, for the reaction between singlet oxygen and several flavonoids. Values of kT determined in deuterated water, ranging from 2.4×107 M−1s−1 to 13.4×107 M−1s−1, for rutin and morin, respectively, and the values measured for kr, ranging from 2.8×105 M−1s−1 to 65.7×105 M−1s−1 for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid. PMID:22802966

  14. Singlet oxygen reactions with flavonoids. A theoretical-experimental study.

    Directory of Open Access Journals (Sweden)

    Javier Morales

    Full Text Available Detection of singlet oxygen emission, λ(max = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T, and the reactive reaction rate constant, k(r, for the reaction between singlet oxygen and several flavonoids. Values of k(T determined in deuterated water, ranging from 2.4×10(7 M(-1 s(-1 to 13.4×10(7 M(-1 s(-1, for rutin and morin, respectively, and the values measured for k(r, ranging from 2.8×10(5 M(-1 s(-1 to 65.7×10(5 M(-1 s(-1 for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

  15. Reversible Photochemical Control of Singlet Oxygen Generation Using Diarylethene Photochromic Switches

    NARCIS (Netherlands)

    Hou, Lili; Zhang, Xiaoyan; Pijper, Thomas C.; Browne, Wesley R.; Feringa, Bernard

    2014-01-01

    Reversible noninvasive control over the generation of singlet oxygen is demonstrated in a bicomponent system comprising a diarylethene photochromic switch and a porphyrin photosensitizer by selective irradiation at distinct wavelengths. The efficient generation of singlet oxygen by the

  16. Photorelease of triplet and singlet oxygen from dioxygen complexes

    Czech Academy of Sciences Publication Activity Database

    Wagnerová, Dana Marie; Lang, Kamil

    2011-01-01

    Roč. 255, 23-24 (2011), s. 2904-2911 ISSN 0010-8545 R&D Projects: GA ČR GAP207/10/1447; GA ČR GAP208/10/1678 Institutional research plan: CEZ:AV0Z40320502 Keywords : singlet oxygen * triplet oxygen * photochemical elimination * photorelease * Dioxygen complex Subject RIV: CA - Inorganic Chemistry Impact factor: 12.110, year: 2011

  17. Spray generator of singlet oxygen for a chemical oxygen-iodine laser

    Czech Academy of Sciences Publication Activity Database

    Jirásek, Vít; Hrubý, Jan; Špalek, Otomar; Čenský, Miroslav; Kodymová, Jarmila

    2010-01-01

    Roč. 100, č. 4 (2010), s. 779-791 ISSN 0946-2171 Grant - others:European Office of Aerospace R&D(US) FA8655-09-1-3091 Institutional research plan: CEZ:AV0Z10100523; CEZ:AV0Z20760514 Keywords : spray generator of singlet oxygen * singlet oxygen * chemical oxygen-iodine laser Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.239, year: 2010

  18. Kinetics of oxygen species in an electrically driven singlet oxygen generator

    Energy Technology Data Exchange (ETDEWEB)

    Azyazov, V.N., E-mail: azyazov@fian.smr.ru [Samara State Aerospace University, 443086 (Russian Federation); Lebedev Physical Institute of RAS, Samara 443011 (Russian Federation); Torbin, A.P.; Pershin, A.A. [Samara State Aerospace University, 443086 (Russian Federation); Lebedev Physical Institute of RAS, Samara 443011 (Russian Federation); Mikheyev, P.A., E-mail: mikheyev@fian.smr.ru [Samara State Aerospace University, 443086 (Russian Federation); Lebedev Physical Institute of RAS, Samara 443011 (Russian Federation); Heaven, M.C., E-mail: mheaven@emory.edu [Emory University, Atlanta, GA 30322 (United States)

    2015-12-16

    Highlights: • Vibrational excitation of O{sub 3} increases the rate constant for O{sub 3} + O{sub 2}(a) → 2O{sub 2}(X) + O. • Vibrationally excited O{sub 3} is produced by the O + O{sub 2}(X) + M → O{sub 3} + M reaction. • Ozone concentrations are impacted by the reactions of vibrationally excited O{sub 3}. • Relevant to ozone concentrations in oxygen discharges and the upper atmosphere. - Abstract: The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O{sub 3}(υ) formed in O + O{sub 2} recombination is thought to be a significant agent in the deactivation of singlet oxygen O{sub 2}(a{sup 1}Δ), oxygen atom removal and ozone formation. It is shown that the process O{sub 3}(υ ⩾ 2) + O{sub 2}(a{sup 1}Δ) → 2O{sub 2} + O is the main O{sub 2}(a{sup 1}Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O{sub 2}(a{sup 1}Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data.

  19. A pulse radiolysis based singlet oxygen luminescence facility

    International Nuclear Information System (INIS)

    Gorman, A.A.; Hamblett, I.; Land, E.J.

    1989-01-01

    In this paper the authors report the first successful time-resolved detection of singlet oxygen, O 2 ( 1 Δ g ), luminescence using the pulse radiolysis technique. The use of this technique (a) to produce high concentrations of solute (S) triplet states in aerated benzene (B) via a combination of channels 1-4 and (b) to subsequently form O 2 ( 1 Δ g ) via channel 5 has already been described. The method complements direct pulsed laser excitation of S in that formation of 3 S*, and therefore of O 2 ( 1 Δ g ), is still efficient in those instances where intersystem crossing (channel 4) is unimportant. In the latter situation a laser-based experiment would require an additional light-absorbing sensitizer which could subsequently transfer triplet energy to high concentrations of S. Such experiments, certainly of a quantitative nature, are usually doomed to failure because of competitive light absorption problems. No such problems exist with pulse radiolysis, and the high available triplet energy of 3 B* (84 kcal mol -1 ) ensures that virtually any solute of interest, in the O 2 ( 1 Δ g ) context, will be efficiently promoted to its triplet state

  20. Singlet oxygen generator for a solar powered chemically pumped iodine laser

    Science.gov (United States)

    Busch, G. E.

    1984-01-01

    The potential of solid phase endoperoxides as a means to produce single-delta oxygen in the gas phase in concentrations useful to chemical oxygen-iodine lasers was investigated. The 1,4 - endoperoxide of ethyl 3- (4-methyl - 1-naphthyl) propanoate was deposited over an indium-oxide layer on a glass plate. Single-delta oxygen was released from the endoperoxide upon heating the organic film by means of an electrical discharge through the conductive indium oxide coating. The evolution of singlet-delta oxygen was determined by measuring the dimol emission signal at 634 nm. Comparison of the measured signal with an analytic model leads to two main conclusions: virtually all the oxygen being evolved is in the singlet-delta state and in the gas phase, and there is no significant quenching other than energy pooling on the time scale of the experiment (approximately 10 msec). The use of solid phase endoperoxide as a singlet-delta oxygen generator for an oxygen-iodine laser appears promising.

  1. New strategies to produce and detect singlet oxygen in a cell

    DEFF Research Database (Denmark)

    Gollmer, Anita

    2012-01-01

    of the general methodology to generate and detect singlet oxygen is currently of great importance in order to better understand the roles played by singlet oxygen in photo-induced cell death. From a mechanistic perspective, experiments performed at the level of a single cell provide unique insight......Singlet oxygen, the first excited electronic state of molecular oxygen, plays a major role in oxygen-dependent photo-induced cell death. In such systems, singlet oxygen is generally produced in a photosensitized process wherein light is absorbed by a molecule (the so-called sensitizer) which......, and that is the perspective of this study. Although the direct optical detection of singlet oxygen by its near IR phosphorescence is the ideal way to monitor this species, it suffers from the problem of weak signal intensity. Fluorescent probes can be a more sensitive way to detect singlet oxygen. The photochemical behavior...

  2. Real-Time Monitoring of Singlet Oxygen and Oxygen Partial Pressure During the Deep Photodynamic Therapy In Vitro.

    Science.gov (United States)

    Li, Weitao; Huang, Dong; Zhang, Yan; Liu, Yangyang; Gu, Yueqing; Qian, Zhiyu

    2016-09-01

    Photodynamic therapy (PDT) is an effective noninvasive method for the tumor treatment. The major challenge in current PDT research is how to quantitatively evaluate therapy effects. To our best knowledge, this is the first time to combine multi-parameter detection methods in PDT. More specifically, we have developed a set of system, including the high-sensitivity measurement of singlet oxygen, oxygen partial pressure and fluorescence image. In this paper, the detection ability of the system was validated by the different concentrations of carbon quantum dots. Moreover, the correlation between singlet oxygen and oxygen partial pressure with laser irradiation was observed. Then, the system could detect the signal up to 0.5 cm tissue depth with 660 nm irradiation and 1 cm tissue depth with 980 nm irradiation by using up-conversion nanoparticles during PDT in vitro. Furthermore, we obtained the relationship among concentration of singlet oxygen, oxygen partial pressure and tumor cell viability under certain conditions. The results indicate that the multi-parameter detection system is a promising asset to evaluate the deep tumor therapy during PDT. Moreover, the system might be potentially used for the further study in biology and molecular imaging.

  3. Singlet Oxygen Sensor Green: Photochemical Behavior in Solution and in a Mammalian Cell

    DEFF Research Database (Denmark)

    Gollmer, Anita; Arnbjerg, Jacob; Blaikie, Frances Helen

    2011-01-01

    The development of efficient and selective luminescent probes for reactive oxygen species, particularly for singlet molecular oxygen, is currently of great importance. In this study, the photochemical behavior of Singlet Oxygen Sensor Green® (SOSG), a commercially available fluorescent probe...... of the reaction between SOSG and singlet oxygen is, itself, an efficient singlet oxygen photosensitizer. Second, SOSG appears to efficiently bind to proteins which, in turn, can influence uptake by a cell as well as behavior in the cell. As such, incorrect use of SOSG can yield misleading data on yields...

  4. Spatial and temporal distribution of singlet oxygen in Lake Superior.

    Science.gov (United States)

    Peterson, Britt M; McNally, Ann M; Cory, Rose M; Thoemke, John D; Cotner, James B; McNeill, Kristopher

    2012-07-03

    A multiyear field study was undertaken on Lake Superior to investigate singlet oxygen ((1)O(2)) photoproduction. Specifically, trends within the lake were examined, along with an assessment of whether correlations existed between chromophoric dissolved organic matter (CDOM) characteristics and (1)O(2) production rates and quantum yields. Quantum yield values were determined and used to estimate noontime surface (1)O(2) steady-state concentrations ([(1)O(2)](ss)). Samples were subdivided into three categories based on their absorbance properties (a300): riverine, river-impacted, or open lake sites. Using calculated surface [(1)O(2)](ss), photochemical half-lives under continuous summer sunlight were calculated for cimetidine, a pharmaceutical whose reaction with (1)O(2) has been established, to be on the order of hours, days, and a week for the riverine, river-impacted, and open lake waters, respectively. Of the CDOM properties investigated, it was found that dissolved organic carbon (DOC) and a300 were the best parameters for predicting production rates of [(1)O(2)](ss). For example, given the correlations found, one could predict [(1)O(2)](ss) within a factor of 4 using a300 alone. Changes in the quantum efficiency of (1)O(2) production upon dilution of river water samples with lake water samples demonstrated that the CDOM found in the open lake is not simply diluted riverine organic matter. The open lake pool was characterized by low absorption coefficient, low fluorescence, and low DOC, but more highly efficient (1)O(2) production and predominates the Lake Superior system spatially. This study establishes that parameters that reflect the quantity of CDOM (e.g., a300 and DOC) correlate with (1)O(2) production rates, while parameters that characterize the absorbance spectrum (e.g., spectral slope coefficient and E2:E3) correlate with (1)O(2) production quantum yields.

  5. Reactive species formed on proteins exposed to singlet oxygen

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan

    2004-01-01

    Singlet oxygen ((1)O(2)) is believed to be generated in biological systems by a range of endogenous processes (e.g. enzymatic and chemical reactions) and exogenous stimuli (e.g. UV or visible light in the presence of a sensitiser). Kinetic data is consistent with proteins being a major target...... hydroperoxides, which can be reduced to the corresponding alcohols; other products arising from radical intermediates can also be generated, particularly in the presence of UV light and metal ions. With His side-chains, poorly characterised peroxides are also formed. Reaction with Met and Cys has been proposed...

  6. Production of Singlet Oxygen in a Non-Self-Sustained Discharge

    International Nuclear Information System (INIS)

    Vasil'eva, A.N.; Klopovskii, K.S.; Kovalev, A.S.; Lopaev, D.V.; Mankelevich, Yu.A.; Popov, N.A.; Rakhimov, A.T.; Rakhimova, T.V.

    2005-01-01

    The production of O 2 (a 1 Δ g ) singlet oxygen in non-self-sustained discharges in pure oxygen and mixtures of oxygen with noble gases (Ar or He) was studied experimentally. It is shown that the energy efficiency of O 2 (a 1 Δ g ) production can be optimized with respect to the reduced electric field E/N. It is shown that the optimal E/N values correspond to electron temperatures of 1.2-1.4 eV. At these E/N values, a decrease in the oxygen percentage in the mixture leads to an increase in the excitation rate of singlet oxygen because of the increase in the specific energy deposition per O 2 molecule. The onset of discharge instabilities not only greatly reduces the energy efficiency of singlet oxygen production but also makes it impossible to achieve high energy deposition in a non-self-sustained discharge. A model of a non-self-sustained discharge in pure oxygen is developed. It is shown that good agreement between the experimental and computed results for a discharge in oxygen over a wide range of reduced electric fields can be achieved only by taking into account the ion component of the discharge current. The cross section for the electron-impact excitation of O 2 (a 1 Δ g ) and the kinetic scheme of the discharge processes with the participation of singlet oxygen are verified by comparing the experimental and computed data on the energy efficiency of the production of O 2 (a 1 Δ g ) and the dynamics of its concentration. It is shown that, in the dynamics of O 2 (a 1 Δ g ) molecules in the discharge afterglow, an important role is played by their deexcitation in a three-body reaction with the participation of O( 3 P) atoms. At high energy depositions in a non-self-sustained discharge, this reaction can reduce the maximal attainable concentration of singlet oxygen. The effect of a hydrogen additive to an Ar : O 2 mixture is analyzed based on the results obtained using the model developed. It is shown that, for actual electron beam current densities, a

  7. Singlet Oxygen Detection Using Red Wine Extracts as Photosensitizers.

    Science.gov (United States)

    Lagunes, Irene; Vázquez-Ortega, Fernanda; Trigos, Ángel

    2017-09-01

    Moderate consumption of red wine provides beneficial effects to health. This is attributed to polyphenol compounds present in wine such as resveratrol, quercetin, gallic acid, rutin, and vanillic acid. The amount of these antioxidants is variable; nevertheless, the main beneficial effects of red wine are attributed to resveratrol. However, it has been found that resveratrol and quercetin are able to photosensitize singlet oxygen generation and conversely, gallic acid acts as quencher. Therefore, and since resveratrol and quercetin are some of the most important antioxidants reported in red wines, the aim of this research was to evaluate the photosensitizing ability of 12 red wine extracts through photo-oxidation of ergosterol. The presence of 1 O 2 was detected by ergosterol conversion into peroxide of ergosterol through 1 H NMR analysis. Our results showed that 10 wine extracts were able to act as photosensitizers in the generation of singlet oxygen. The presence of 1 O 2 can damage other compounds of red wine and cause possible organoleptic alterations. Finally, although the reaction conditions employed in this research do not resemble the inherent conditions in wine making processing or storing, or even during its consumption, this knowledge could be useful to prevent possible pro-oxidant effects and avoid detrimental effects in red wines. © 2017 Institute of Food Technologists®.

  8. X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy: determination of singlet oxygen quantum yield

    OpenAIRE

    Clement, Sandhya; Deng, Wei; Camilleri, Elizabeth; Wilson, Brian C.; Goldys, Ewa M.

    2016-01-01

    Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8?keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79???0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result ...

  9. Non-self-sustained electric discharge in oxygen gas mixtures: singlet delta oxygen production

    CERN Document Server

    Ionin, A A; Kotkov, A A; Kochetov, I V; Napartovich, A P; Seleznev, L V; Sinitsyn, D V; Hager, G D

    2003-01-01

    The possibility of obtaining a high specific input energy in an electron-beam sustained discharge ignited in oxygen gas mixtures O sub 2 : Ar : CO (or H sub 2) at the total gas pressures of 10-100 Torr was experimentally demonstrated. The specific input energy per molecular component exceeded approx 6 kJ l sup - sup 1 atm sup - sup 1 (150 kJ mol sup - sup 1) as a small amount of carbon monoxide was added into a gas mixture of oxygen and argon. It was theoretically demonstrated that one might expect to obtain a singlet delta oxygen yield of 25% exceeding its threshold value needed for an oxygen-iodine laser operation at room temperature, when maintaining a non-self-sustained discharge in oxygen gas mixtures with molecular additives CO, H sub 2 or D sub 2. The efficiency of singlet delta oxygen production can be as high as 40%.

  10. Singlet oxygen production by combining erythrosine and halogen light for photodynamic inactivation of Streptococcus mutans.

    Science.gov (United States)

    Fracalossi, Camila; Nagata, Juliana Yuri; Pellosi, Diogo Silva; Terada, Raquel Sano Suga; Hioka, Noboru; Baesso, Mauro Luciano; Sato, Francielle; Rosalen, Pedro Luiz; Caetano, Wilker; Fujimaki, Mitsue

    2016-09-01

    Photodynamic inactivation of microorganisms is based on a photosensitizing substance which, in the presence of light and molecular oxygen, produces singlet oxygen, a toxic agent to microorganisms and tumor cells. This study aimed to evaluate singlet oxygen quantum yield of erythrosine solutions illuminated with a halogen light source in comparison to a LED array (control), and the photodynamic effect of erythrosine dye in association with the halogen light source on Streptococcus mutans. Singlet oxygen quantum yield of erythrosine solutions was quantified using uric acid as a chemical-probe in an aqueous solution. The in vitro effect of the photodynamic antimicrobial activity of erythrosine in association with the halogen photopolimerizing light on Streptococcus mutans (UA 159) was assessed during one minute. Bacterial cultures treated with erythrosine alone served as negative control. Singlet oxygen with 24% and 2.8% degradation of uric acid in one minute and a quantum yield of 0.59 and 0.63 was obtained for the erythrosine samples illuminated with the halogen light and the LED array, respectively. The bacterial cultures with erythrosine illuminated with the halogen light presented a decreased number of CFU mL(-1) in comparison with the negative control, with minimal inhibitory concentrations between 0.312 and 0.156mgmL(-1). The photodynamic response of erythrosine induced by the halogen light was capable of killing S. mutans. Clinical trials should be conducted to better ascertain the use of erythrosine in association with halogen light source for the treatment of dental caries. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Singlet Oxygen Sensor Green: Photochemical Behavior in Solution and in a Mammalian Cell

    DEFF Research Database (Denmark)

    Gollmer, Anita; Arnbjerg, Jacob; Blaikie, Frances Helen

    2011-01-01

    The development of efficient and selective luminescent probes for reactive oxygen species, particularly for singlet molecular oxygen, is currently of great importance. In this study, the photochemical behavior of Singlet Oxygen Sensor Green® (SOSG), a commercially available fluorescent probe...... for singlet oxygen, was examined. Despite published claims to the contrary, the data presented herein indicate that SOSG can, in fact, be incorporated into a living mammalian cell. However, for a number of reasons, caution must be exercised when using SOSG. First, it is shown that the immediate product...... of the reaction between SOSG and singlet oxygen is, itself, an efficient singlet oxygen photosensitizer. Second, SOSG appears to efficiently bind to proteins which, in turn, can influence uptake by a cell as well as behavior in the cell. As such, incorrect use of SOSG can yield misleading data on yields...

  12. Singlet oxygen oxygenation of enol ethers; the synthesis of optically active 1,2-dioxetanes. II

    NARCIS (Netherlands)

    Meijer, E.W.; Wynberg, H.

    1979-01-01

    (+)-(Methoxymethylene)fenchane I (R = H, R1 = OMe) on singlet O oxidn. gave dioxetanes II and III, which on thermal decompn. underwent chemiluminescence in which (+)-fenchone was the only chemiluminescent species at lmax 420 nm. Photosensitized oxygenation of I (R = OMe, R1 = H) also gave 2 isomeric

  13. Pulsed electron-beam-sustained discharge in oxygen-containing gas mixtures: electrical characteristics, spectroscopy,and singlet oxygen yield

    International Nuclear Information System (INIS)

    Vagin, Nikolai P; Ionin, Andrei A; Klimachev, Yu M; Kotkov, A A; Podmar'kov, Yu P; Seleznev, L V; Sinitsyn, D V; Frolov, M P; Yuryshev, Nikolai N; Kochetov, Igor' V; Napartovich, A P; Hager, G D

    2004-01-01

    The electrical and spectroscopic characteristics of electron-beam-sustained discharge (EBSD) in oxygen and oxygen-containing gas mixtures are studied experimentally under gas pressures up to 100 Torr in a large excitation volume (∼18 L). It is shown that the EBSD in pure oxygen and its mixtures with inert gases is unstable and is characterised by a small specific energy contribution. The addition of small amounts (∼1%-10%) of carbon monoxide or hydrogen to oxygen or its mixtures with inert gases considerably improves the stability of the discharge, while the specific energy contribution W increases by more then an order of magnitude, achieving ∼6.5 kJ L -1 atm -1 per molecular component of the gas mixture. A part of the energy supplied to the EBSD is spent to excite vibrational levels of molecular additives. This was demonstrated experimentally by the initiation of a CO laser based on the O 2 : Ar : CO = 1 : 1 : 0.1 mixture. Experimental results on spectroscopy of the excited electronic states O 2 (a 1 Δ g ) and O 2 (b 1 Σ g + ), of oxygen formed in the EBSD are presented. A technique was worked out for measuring the concentration of singlet oxygen in the O 2 (a 1 Δ g ) state in the afterglow of the pulsed EBSD by comparing with the radiation intensity of singlet oxygen of a given concentration produced in a chemical generator. Preliminary measurements of the singlet-oxygen yield in the EBSD show that its value ∼3% for W ∼ 1.0 kJ L -1 atm -1 is in agreement with the theoretical estimate. Theoretical calculations performed for W ∼ 6.5 kJ L -1 atm -1 at a fixed temperature show that the singlet-oxygen yield may be ∼20%, which is higher than the value required to achieve the lasing threshold in an oxygen-iodine laser at room temperature. (laser applications and other topics in quantum electronics)

  14. Centrifugal spray generator of singlet oxygen for a chemical oxygen-iodine laser

    Czech Academy of Sciences Publication Activity Database

    Špalek, Otomar; Hrubý, Jan; Čenský, Miroslav; Jirásek, Vít; Kodymová, Jarmila

    2010-01-01

    Roč. 100, č. 4 (2010), s. 793-802 ISSN 0946-2171 Grant - others:European Office of Aerospace R&D(US) FA8655-09-1-3091 Institutional research plan: CEZ:AV0Z10100523; CEZ:AV0Z20760514 Keywords : centrifugal generator of singlet oxygen * chemical oxygen-iodine laser Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.239, year: 2010

  15. Photo-excitation of carotenoids causes cytotoxicity via singlet oxygen production

    International Nuclear Information System (INIS)

    Yoshii, Hiroshi; Yoshii, Yukie; Asai, Tatsuya; Furukawa, Takako; Takaichi, Shinichi; Fujibayashi, Yasuhisa

    2012-01-01

    Highlights: ► Some photo-excited carotenoids have photosensitizing ability. ► They are able to produce ROS. ► Photo-excited fucoxanthin can produce singlet oxygen through energy transfer. -- Abstract: Carotenoids, natural pigments widely distributed in algae and plants, have a conjugated double bond system. Their excitation energies are correlated with conjugation length. We hypothesized that carotenoids whose energy states are above the singlet excited state of oxygen (singlet oxygen) would possess photosensitizing properties. Here, we demonstrated that human skin melanoma (A375) cells are damaged through the photo-excitation of several carotenoids (neoxanthin, fucoxanthin and siphonaxanthin). In contrast, photo-excitation of carotenoids that possess energy states below that of singlet oxygen, such as β-carotene, lutein, loroxanthin and violaxanthin, did not enhance cell death. Production of reactive oxygen species (ROS) by photo-excited fucoxanthin or neoxanthin was confirmed using a reporter assay for ROS production with HeLa Hyper cells, which express a fluorescent indicator protein for intracellular ROS. Fucoxanthin and neoxanthin also showed high cellular penetration and retention. Electron spin resonance spectra using 2,2,6,6-tetramethil-4-piperidone as a singlet oxygen trapping agent demonstrated that singlet oxygen was produced via energy transfer from photo-excited fucoxanthin to oxygen molecules. These results suggest that carotenoids such as fucoxanthin, which are capable of singlet oxygen production through photo-excitation and show good penetration and retention in target cells, are useful as photosensitizers in photodynamic therapy for skin disease.

  16. Mechanism of singlet oxygen deactivation in an electric discharge oxygen – iodine laser

    Energy Technology Data Exchange (ETDEWEB)

    Azyazov, V N; Mikheyev, P A; Torbin, A P [Samara Branch of the P.N. Lebedev Physical Institute, Russian Academy of Sciences, Samara (Russian Federation); Pershin, A A [S.P. Korolev Samara State Aerospace University, Samara (Russian Federation); Heaven, M C [Emory University, Atlanta, GA, 30322 (United States)

    2014-12-31

    We have determined the influence of the reaction of molecular singlet oxygen with a vibrationally excited ozone molecule O{sub 2}(a {sup 1}Δ) + O{sub 3}(ν) → 2O{sub 2} + O on the removal rate of O{sub 2}(a {sup 1}Δ) in an electric-discharge-driven oxygen – iodine laser. This reaction has been shown to be a major channel of O{sub 2}(a {sup 1}Δ) loss at the output of an electric-discharge singlet oxygen generator. In addition, it can also contribute significantly to the loss of O{sub 2}(a {sup 1}Δ) in the discharge region of the generator. (lasers)

  17. Cytotoxicity But No Mutagenicity In Bacteria With Externally Generated Singlet Oxygen

    Science.gov (United States)

    Midden, W. Robert; Dahl, Thomas A.; Hartman, Philip E.

    1988-02-01

    Singlet oxygen is believed to be an important intermediate responsible for the cytotoxicity of HpD phototherapy. It has been recognized as a possible intermediate in photosensitization for more than 20 years. However, it has been difficult to obtain conclusive evidence of its biological characteristics in the past because most of the methods available for its generation that are compatible with biological systems also generate other reactive intermediates whose effects are difficult to distinguish from singlet oxygen. We have used a recently devised separated-surface-sensi-tizer (S-S-S) system for singlet oxygen generation' to measure the cytotoxicity and mutagenicity of singlet oxygen in bacteria. The S-S-S system employs rose bengal as a sensitizer immobilized on one surface of a glass plate. The glass plate is placed sensitizer-side down a small distance (plate is illuminated from above to generate singlet oxygen at the surface of the sensitizer. The singlet oxygen thus generated can diffuse the short dis-tance to the surface of the membrane to react with the bacteria. Because of the short lifetime of singlet oxygen in air, increasing the distance between the sensitizer and the membrane causes a decline in the amount of singlet oxygen reaching the membrane according to a function derived from the Einstein-Smoluchowski equation for net displacement by diffusion. Plotting the log of the effect measured (e.g., cytotoxicity) vs. the square of the distance gives a straight line. The slope of this line can be used to calculate the gas phase half life of the intermediate responsible for the observed effects. We have found that bacteria are rapidly killed in the illuminated S-S-S system and that the gas phase half life of the agent responsible for cell killing is the same as that of singlet oxygen. This observation and other simple chemical tests have conclusively estab-lished that singlet oxygen is responsible for the cytotoxicity observed with bacteria. Dosimetry

  18. Bromorhodamines - new singlet oxygen photosensitizers for oxidative water and wastewater treatment

    Energy Technology Data Exchange (ETDEWEB)

    Slivka, L.; Alekseeva, V.; Kuznetsova, N.; Marinina, L.; Savvina, L.; Kaliya, O.; Lukyanets, E.; Vorozhtsov, G. [Organic Intermediates and Dyes Inst., Moscow (Russian Federation); Krasnovsky, A.; Butorina, D. [Inst. of Biochemistry RAS, Moscow (Russian Federation)

    2003-07-01

    The cationic mono-, di- and tetrabromoderivatives of rhodamine 123 have been synthesized and studied as sensitizers for singlet oxygen formation in application for oxidative water treatment. Singlet oxygen quantum yields for compounds under investigation have been determined by using its near IR luminescence at 1270 nm. Bromorhodamines123 have been shown to sensitize the formation of singlet oxygen in aqueous solution with high quantum yields. Efficient oxidation of tryptophan in aqueous solutions sensitized by dibromorhodamine 123 has been demonstrated. This dye was tested as sensitizer for photodynamic treatment of water contaminated with coliform bacteria. It was shown to participate in the photosensitization of coliform bacteria, resulting in their efficient killing. (orig.)

  19. Wavelength dependence of the efficiency of singlet oxygen generation upon photoexcitation of photosensitizers

    Directory of Open Access Journals (Sweden)

    Starukhin A.

    2017-01-01

    Full Text Available The dependence of the efficiency of singlet oxygen (1Δg generation upon excitation of photosensitizer at different wavelength was observed for several derivatives of palladium porphyrin in carbon tetrachloride. The efficiency of singlet oxygen generation upon excitation in a blue region of the spectrum (Soret band exceeds by several times the efficiency at excitation in the red spectral region (Q band. The effect of enhancement of singlet oxygen generation upon CW photoexcitation to Soret band of photosensitizer may be explained by influence of high laying triplet states of a donor molecule on the triplet-triplet energy transfer.

  20. Regulation of singlet oxygen-induced apoptosis by cytosolic NADP+-dependent isocitrate dehydrogenase.

    Science.gov (United States)

    Kim, Sun Yee; Lee, Su Min; Tak, Jean Kyoung; Choi, Kyeong Sook; Kwon, Taeg Kyu; Park, Jeen-Woo

    2007-08-01

    Singlet oxygen is a highly reactive form of molecular oxygen that may harm living systems by oxidizing critical cellular macromolecules and it also promotes deleterious processes such as cell death. Recently, we demonstrated that the control of redox balance and the cellular defense against oxidative damage are the primary functions of cytosolic NADP(+)-dependent isocitrate dehydrogenase (IDPc) through supplying NADPH for antioxidant systems. In this report, we demonstrate that modulation of IDPc activity in HL-60 cells regulates singlet oxygen-induced apoptosis. When we examined the protective role of IDPc against singlet oxygen-induced apoptosis with HL-60 cells transfected with the cDNA for mouse IDPc in sense and antisense orientations, a clear inverse relationship was observed between the amount of IDPc expressed in target cells and their susceptibility to apoptosis. The results suggest that IDPc plays an important protective role in apoptosis of HL-60 cells induced by singlet oxygen.

  1. Label-free electrochemical detection of singlet oxygen protein damage

    International Nuclear Information System (INIS)

    Vargová, Veronika; Giménez, Rodrigo E.; Černocká, Hana; Trujillo, Diana Chito; Tulli, Fiorella; Zanini, Verónica I. Paz; Paleček, Emil; Borsarelli, Claudio D.; Ostatná, Veronika

    2016-01-01

    Oxidative damage of proteins results in changes of their structures and functions. In this work, the singlet oxygen ( 1 O 2 )-mediated oxidation of bovine serum albumin (BSA) and urease by blue-light photosensitization of the tris(2,2′-bipyridine)ruthenium(II) cation [Ru(bpy) 3 ] 2+ was studied by square wave voltammetry at glassy carbon electrode and by constant current chronopotentiometry at mercury electrode. Small changes in voltammetric oxidation Tyr and Trp peaks did not indicate significant changes in the BSA structure after photo-oxidation at carbon electrode. On the other hand chronopotentiometric peak H of BSA at HMDE increased during blue-light photosensitization, indicating that photo-oxidized BSA was more susceptible to the electric field-induced denaturation than non-oxidized native BSA. Similar results were obtained for urease, where enzymatic activity was also evaluated. The present results show the capability of label- and reagent-free electrochemical methods to detect oxidative changes in proteins. We believe that these methods will become important tools for detection of various protein damages.

  2. Singlet oxygen-induced oxidation of alkylthiocarboxylic acids

    International Nuclear Information System (INIS)

    Celuch, M.; Pogocki, D.; Enache, M.

    2006-01-01

    Singlet oxygen ( 1 O 2 ) could be generated in biological systems by endogenous and exogenous processes (e.g. enzymatic and chemical reactions, UV or visible light in the presence of a sensitizer). Numerous data show that proteins are the major targets of 1 O 2 -induced damage in the living cells. In particular, reaction of 1 O 2 with thioether sulphur of methionine (Met) leads to the formation of persulphoxide >S (+) O-O (-) which is in equilibrium with superoxide radical-anion (O 2 ·- ) and respective sulphur-centered-radical-cation >S ·+ . In presented work, investigation the mechanisms of deprotonation and decarboxylation of the S ·+ - the irreversible processes, which competes with the formation of sulphoxide. Using thioethers dissevering by the number and positions of carboxylate groups it has been shown that efficiency of both decarboxylation and deprotonation could be influenced by various factors such as neighbouring group participation and environmental effects. The observed influence of carboxylate groups in β-position relative to the sulphur on the efficiency of decarboxylation suggests furthermore that they may also catalyze decarboxylation of α-positioned carboxylate in a manner similar to hydroxide anion

  3. Singlet Delta Oxygen: A Quantitative Analysis Using Off-Axis Integrated-Cavity-Output-Spectroscopy (ICOS)

    National Research Council Canada - National Science Library

    Gallagher, Jeffrey E

    2006-01-01

    .... The method is based on off-axis integrated-cavity-output spectroscopy (ICOS). The primary goal for this research effort is to utilize the ICOS technique and demonstrate its ability to provide quantitative data of singlet delta oxygen...

  4. Molecular Tuning of Phenylene-Vinylene Derivatives for Two-Photon Photosensitized Singlet Oxygen Production

    DEFF Research Database (Denmark)

    Nielsen, Christian B.; Arnbjerg, Jacob; Johnsen, Mette

    2009-01-01

    Substituent-dependent features and properties of the sensitizer play an important role in the photosensitized production of singlet oxygen, O2(a1Δg). In this work, we systematically examine the effect of molecular changes in the sensitizer on the efficiency of singlet oxygen production using......, as the sensitizer, oligophenylene-vinylene derivatives designed to optimally absorb light in a nonlinear two-photon process. We demonstrate that one cannot always rely on rule-of-thumb guidelines when attempting to construct efficient two-photon singlet oxygen sensitizers. Rather, as a consequence of behavior...... that can deviate from the norm, a full investigation of the photophysical properties of the system is generally required. For example, it is acknowledged that the introduction of a ketone moiety to the sensitizer chromophore often results in more efficient production of singlet oxygen. However, we show...

  5. Highly sensitive time resolved singlet oxygen luminescence detection using LEDs as the excitation source

    International Nuclear Information System (INIS)

    Hackbarth, S; Schlothauer, J; Preuss, A; Röder, B

    2013-01-01

    For the first time singlet oxygen luminescence kinetics in living cells were detected at high precision using LED light for excitation. As LED technology evolves, the light intensity emitted by standard LEDs allows photosensitized singlet oxygen luminescence detection in solution and cell suspensions. We present measurements superior to those of most actual laser powered setups regarding precision of singlet oxygen kinetics in solutions and cell suspensions. Data presented here show that LED based setups allow the determination of the photosensitizer triplet and singlet oxygen decay times in vitro with an accuracy of 0.1 μs. This enables monitoring of the photosensitizer efficiency and interaction with the cellular components using illumination doses small enough not to cause cell death. (letter)

  6. Exposure of vitamins to UVB and UVA radiation generates singlet oxygen.

    Science.gov (United States)

    Knak, Alena; Regensburger, Johannes; Maisch, Tim; Bäumler, Wolfgang

    2014-05-01

    Deleterious effects of UV radiation in tissue are usually attributed to different mechanisms. Absorption of UVB radiation in cell constituents like DNA causes photochemical reactions. Absorption of UVA radiation in endogenous photosensitizers like vitamins generates singlet oxygen via photosensitized reactions. We investigated two further mechanisms that might be involved in UV mediated cell tissue damage. Firstly, UVB radiation and vitamins also generate singlet oxygen. Secondly, UVB radiation may change the chemical structure of vitamins that may change the role of such endogenous photosensitizers in UVA mediated mechanisms. Vitamins were irradiated in solution using monochromatic UVB (308 nm) or UVA (330, 355, or 370 nm) radiation. Singlet oxygen was directly detected and quantified by its luminescence at 1270 nm. All investigated molecules generated singlet oxygen with a quantum yield ranging from 0.007 (vitamin D3) to 0.64 (nicotinamide) independent of the excitation wavelength. Moreover, pre-irradiation of vitamins with UVB changed their absorption in the UVB and UVA spectral range. Subsequently, molecules such as vitamin E and vitamin K1, which normally exhibit no singlet oxygen generation in the UVA, now produce singlet oxygen when exposed to UVA at 355 nm. This interplay of different UV sources is inevitable when applying serial or parallel irradiation with UVA and UVB in experiments in vitro. These results should be of particular importance for parallel irradiation with UVA and UVB in vivo, e.g. when exposing the skin to solar radiation.

  7. Influence of nitrogen oxides NO and NO2 on singlet delta oxygen production in pulsed discharge

    International Nuclear Information System (INIS)

    Ionin, A A; Klimachev, Yu M; Kozlov, A Yu; Kotkov, A A; Rulev, O A; Seleznev, L V; Sinitsyn, D V; Vagin, N P; Yuryshev, N N; Kochetov, I V; Napartovich, A P

    2009-01-01

    The influence of nitrogen oxides NO and NO 2 on the specific input energy (SIE) and the time behaviour of singlet delta oxygen (SDO) luminescence excited by a pulsed e-beam sustained discharge in oxygen were experimentally and theoretically studied. NO and NO 2 addition into oxygen results in a small increase and decrease in the SIE, respectively, the latter being connected with a large energy of electron affinity to NO 2 . The addition of 0.1-0.3% nitrogen oxides was experimentally and theoretically demonstrated to result in a notable enhancement of the SDO lifetime, which is related to a decrease in the atomic oxygen concentration in afterglow. It was experimentally demonstrated that to get a high SDO concentration at the gas pressure 30-60 Torr for a time interval of less than ∼0.5 s one needs to add not less than 0.2% nitrogen oxides into oxygen. The temperature dependence of the relaxation constant for SDO quenching by unexcited oxygen was estimated by using experimental data on the time behaviour of SDO luminescence.

  8. The generation of singlet oxygen (o(2)) by the nitrodiphenyl ether herbicide oxyfluorfen is independent of photosynthesis.

    Science.gov (United States)

    Haworth, P; Hess, F D

    1988-03-01

    The mechanism of action of the p-nitrodiphenyl ether herbicides has remained ambiguous because of conflicting reports in the literature. The diphenyl ether herbicide oxyfluorfen causes a light induced consumption of oxygen which resembles the electron acceptor reaction of paraquat. However, this reaction is not linked to the transport of electrons through photosystem I. This conclusion is based on the observation that the rate of oxygen consumption, in the presence of oxyfluorfen, does not demonstrate a first order rate dependence on light intensity. Using the bleaching of N,N-dimethyl p-nitrosoaniline as a specific detector of singlet oxygen, we demonstrate that oxyfluorfen is a potent generator of this toxic radical. The production of singlet oxygen occurs in the presence of inhibitors of photosynthetic electron transport (oxyfluorfen at 10(-4) molar and paraquat) and also under temperature conditions (3 degrees C) which prevent electron transport. This light induced reaction results in oxygen consumption and is the primary cause of lethality for oxyfluorfen. The production of singlet oxygen occurs rapidly and at low herbicide concentrations (10(-9) molar). The reaction occurs without photosynthetic electron transport but does require an intact thylakoid membrane.

  9. The Generation of Singlet Oxygen (1O2) by the Nitrodiphenyl Ether Herbicide Oxyfluorfen Is Independent of Photosynthesis

    Science.gov (United States)

    Haworth, Phil; Hess, F. Dan

    1988-01-01

    The mechanism of action of the p-nitrodiphenyl ether herbicides has remained ambiguous because of conflicting reports in the literature. The diphenyl ether herbicide oxyfluorfen causes a light induced consumption of oxygen which resembles the electron acceptor reaction of paraquat. However, this reaction is not linked to the transport of electrons through photosystem I. This conclusion is based on the observation that the rate of oxygen consumption, in the presence of oxyfluorfen, does not demonstrate a first order rate dependence on light intensity. Using the bleaching of N,N-dimethyl p-nitrosoaniline as a specific detector of singlet oxygen, we demonstrate that oxyfluorfen is a potent generator of this toxic radical. The production of singlet oxygen occurs in the presence of inhibitors of photosynthetic electron transport (oxyfluorfen at 10−4 molar and paraquat) and also under temperature conditions (3°C) which prevent electron transport. This light induced reaction results in oxygen consumption and is the primary cause of lethality for oxyfluorfen. The production of singlet oxygen occurs rapidly and at low herbicide concentrations (10−9 molar). The reaction occurs without photosynthetic electron transport but does require an intact thylakoid membrane. PMID:16665968

  10. Cellular defense against singlet oxygen-induced oxidative damage by cytosolic NADP+-dependent isocitrate dehydrogenase.

    Science.gov (United States)

    Kim, Sun Yee; Park, Jeen-Woo

    2003-03-01

    Singlet oxygen (1O2) is a highly reactive form of molecular oxygen that may harm living systems by oxidizing critical cellular macromolecules. Recently, we have shown that NADP+-dependent isocitrate dehydrogenase is involved in the supply of NADPH needed for GSH production against cellular oxidative damage. In this study, we investigated the role of cytosolic form of NADP+-dependent isocitrate dehydrogenase (IDPc) against singlet oxygen-induced cytotoxicity by comparing the relative degree of cellular responses in three different NIH3T3 cells with stable transfection with the cDNA for mouse IDPc in sense and antisense orientations, where IDPc activities were 2.3-fold higher and 39% lower, respectively, than that in the parental cells carrying the vector alone. Upon exposure to singlet oxygen generated from photoactivated dye, the cells with low levels of IDPc became more sensitive to cell killing. Lipid peroxidation, protein oxidation, oxidative DNA damage and intracellular peroxide generation were higher in the cell-line expressing the lower level of IDPc. However, the cells with the highly over-expressed IDPc exhibited enhanced resistance against singlet oxygen, compared to the control cells. The data indicate that IDPc plays an important role in cellular defense against singlet oxygen-induced oxidative injury.

  11. Singlet oxygen feedback delayed fluorescence of protoporphyrin IX in organic solutions.

    Science.gov (United States)

    Vinklárek, Ivo S; Scholz, Marek; Dědic, Roman; Hála, Jan

    2017-04-12

    Delayed fluorescence (DF) of protoporphyrin IX (PpIX) has been recently proposed as a tool for monitoring of mitochondrial oxygen tension in vivo as well as for observation of the effectiveness of photodynamic therapy (PDT) [E. G. Mik, Anesth. Analg., 2013, 117, 834-346; F. Piffaretti et al., J. Biomed. Opt., 2012, 17, 115007]. However, the efficiency of the mechanism of thermal activation (E-type DF), which was considered in the papers, is limited due to a large energy gap between the first excited singlet and the first triplet state of PpIX at room or body temperatures. Moreover, the energy gap is roughly equal to other porphyrinoid photosensitizers that generate DF mostly through the Singlet Oxygen Feedback-Induced mechanism (SOFDF) under certain conditions [M. Scholz and R. Dědic, Singlet Oxygen: Applications in Biosciences and Nanosciences, 2016, vol. 2, pp. 63-81]. The mechanisms of delayed fluorescence of PpIX dissolved either in dimethylformamide (DMF) or in the mixture of DMF with ethylene glycol (EG) were investigated at atmospheric partial pressure of oxygen by means of a simultaneous time-resolved detection of 1 O 2 phosphorescence and PpIX DF which makes a direct comparison of the kinetics and lifetimes of both the luminescence channels possible. Samples of PpIX (100 μM) exhibit concave DF kinetics, which is a typical footprint of the SOFDF mechanism. The dramatic decrease in the DF intensity after adding a selective 1 O 2 quencher sodium azide (NaN 3 , 10 mM) proves that >90% of DF is indeed generated through SOFDF. Moreover, the analysis of the DF kinetics in the presence of NaN 3 implies that the second significant mechanism of DF generation is the triplet-triplet annihilation (P-type DF). The bimolecular mechanism of DF was further confirmed by the decrease of the DF intensity in the more viscous mixture DMF/EG and by the increase of the ratio of DF to the prompt fluorescence (PF) intensity with the increasing excitation intensity. These results

  12. Development of Singlet Oxygen Luminescence Kinetics during the Photodynamic Inactivation of Green Algae

    Directory of Open Access Journals (Sweden)

    Tobias Bornhütter

    2016-04-01

    Full Text Available Recent studies show the feasibility of photodynamic inactivation of green algae as a vital step towards an effective photodynamic suppression of biofilms by using functionalized surfaces. The investigation of the intrinsic mechanisms of photodynamic inactivation in green algae represents the next step in order to determine optimization parameters. The observation of singlet oxygen luminescence kinetics proved to be a very effective approach towards understanding mechanisms on a cellular level. In this study, the first two-dimensional measurement of singlet oxygen kinetics in phototrophic microorganisms on surfaces during photodynamic inactivation is presented. We established a system of reproducible algae samples on surfaces, incubated with two different cationic, antimicrobial potent photosensitizers. Fluorescence microscopy images indicate that one photosensitizer localizes inside the green algae while the other accumulates along the outer algae cell wall. A newly developed setup allows for the measurement of singlet oxygen luminescence on the green algae sample surfaces over several days. The kinetics of the singlet oxygen luminescence of both photosensitizers show different developments and a distinct change over time, corresponding with the differences in their localization as well as their photosensitization potential. While the complexity of the signal reveals a challenge for the future, this study incontrovertibly marks a crucial, inevitable step in the investigation of photodynamic inactivation of biofilms: it shows the feasibility of using the singlet oxygen luminescence kinetics to investigate photodynamic effects on surfaces and thus opens a field for numerous investigations.

  13. Parabanic acid is the singlet oxygen specific oxidation product of uric acid.

    Science.gov (United States)

    Iida, Sayaka; Ohkubo, Yuki; Yamamoto, Yorihiro; Fujisawa, Akio

    2017-11-01

    Uric acid quenches singlet oxygen physically or reacts with it, but the oxidation product has not been previously characterized. The present study determined that the product is parabanic acid, which was confirmed by LC/TOFMS analysis. Parabanic acid was stable at acidic pH (acid at neutral or alkaline pH. The total yields of parabanic acid and oxaluric acid based on consumed uric acid were ~100% in clean singlet oxygen production systems such as UVA irradiation of Rose Bengal and thermal decomposition of 3-(1,4-dihydro-1,4-epidioxy-4-methyl-1-naphthyl)propionic acid. However, the ratio of the amount of uric acid consumed to the total amount of singlet oxygen generated was less than 1/180, indicating that most of the singlet oxygen was physically quenched. The total yields of parabanic acid and oxaluric acid were high in the uric acid oxidation systems with hydrogen peroxide plus hypochlorite or peroxynitrite. They became less than a few percent in peroxyl radical-, hypochlorite- or peroxynitrite-induced oxidation of uric acid. These results suggest that parabanic acid could be an in vivo probe of singlet oxygen formation because of the wide distribution of uric acid in human tissues and extracellular spaces. In fact, sunlight exposure significantly increased human skin levels of parabanic acid.

  14. Microscopic time-resolved imaging of singlet oxygen by delayed fluorescence in living cells.

    Science.gov (United States)

    Scholz, Marek; Dědic, Roman; Hála, Jan

    2017-11-08

    Singlet oxygen is a highly reactive species which is involved in a number of processes, including photodynamic therapy of cancer. Its very weak near-infrared emission makes imaging of singlet oxygen in biological systems a long-term challenge. We address this challenge by introducing Singlet Oxygen Feedback Delayed Fluorescence (SOFDF) as a novel modality for semi-direct microscopic time-resolved wide-field imaging of singlet oxygen in biological systems. SOFDF has been investigated in individual fibroblast cells incubated with a well-known photosensitizer aluminium phthalocyanine tetrasulfonate. The SOFDF emission from the cells is several orders of magnitude stronger and much more readily detectable than the very weak near-infrared phosphorescence of singlet oxygen. Moreover, the analysis of SOFDF kinetics enables us to estimate the lifetimes of the involved excited states. Real-time SOFDF images with micrometer spatial resolution and submicrosecond temporal-resolution have been recorded. Interestingly, a steep decrease in the SOFDF intensity after the photodynamically induced release of a photosensitizer from lysosomes has been demonstrated. This effect could be potentially employed as a valuable diagnostic tool for monitoring and dosimetry in photodynamic therapy.

  15. Cytometric quantification of singlet oxygen in the human malaria parasite Plasmodium falciparum

    NARCIS (Netherlands)

    Butzloff, Sabine; Groves, Matthew R; Wrenger, Carsten; Müller, Ingrid B

    The malaria parasite Plasmodium falciparum proliferates within human erythrocytes and is thereby exposed to a variety of reactive oxygen species (ROS) such as hydrogen peroxide, hydroxyl radical, superoxide anion, and highly reactive singlet oxygen ((1)O(2)). While most ROS are already well studied

  16. Photosensitized production of singlet oxygen: spatially-resolved optical studies in single cells

    DEFF Research Database (Denmark)

    Breitenbach, Thomas; Kuimova, Marina; Gbur, Peter

    2009-01-01

    be monitored using viability assays. Time- and spatially-resolved optical measurements of both singlet oxygen and its precursor, the excited state sensitizer, reflect the complex and dynamic morphology of the cell. These experiments help elucidate photoinduced, oxygen-dependent events that compromise cell...

  17. Bactericidal action of photogenerated singlet oxygen from photosensitizers used in plaque disclosing agents.

    Directory of Open Access Journals (Sweden)

    Kirika Ishiyama

    Full Text Available BACKGROUND: Photodynamic therapy (PDT has been suggested as an efficient clinical approach for the treatment of dental plaque in the field of dental care. In PDT, once the photosensitizer is irradiated with light of a specific wavelength, it transfers the excitation energy to molecular oxygen, which gives rise to singlet oxygen. METHODOLOGY/PRINCIPAL FINDINGS: Since plaque disclosing agents usually contain photosensitizers such as rose bengal, erythrosine, and phloxine, they could be used for PTD upon photoactivation. The aim of the present study is to compare the ability of these three photosensitizers to produce singlet oxygen in relation to their bactericidal activity. The generation rates of singlet oxygen determined by applying an electron spin resonance technique were in the order phloxine > erythrosine ≒ rose bengal. On the other hand, rose bengal showed the highest bactericidal activity against Streptococcus mutans, a major causative pathogen of caries, followed by erythrosine and phloxine, both of which showed activity similar to each other. One of the reasons for the discrepancy between the singlet oxygen generating ability and bactericidal activity was the incorporation efficiency of the photosensitizers into the bacterial cells. The incorporation rate of rose bengal was the highest among the three photosensitizers examined in the present study, likely leading to the highest bactericidal activity. Meanwhile, the addition of L-histidine, a singlet oxygen quencher, cancelled the bactericidal activity of any of the three photoactivated photosensitizers, proving that singlet oxygen was responsible for the bactericidal action. CONCLUSIONS: It is strongly suggested that rose bengal is a suitable photosensitizer for the plaque disclosing agents as compared to the other two photosensitizers, phloxine and erythrosine, when used for PDT.

  18. Inactivation of Neurospora crassa conidia by singlet molecular oxygen generated by a photosensitized reaction

    International Nuclear Information System (INIS)

    Shimizu, M.; Egashira, T.; Takahama, U.

    1979-01-01

    Photodynamic damage of Neurospora crassa conidia was studied in the presence of the photosensitizing dye, toluidine blue O. Conidia which germinated to form colonies decreased in number as irradiation time became longer. The photoinactivation of conidia was suppressed by azide, bovine serum albumin, and histidine, and was stimulated in deuterium oxide. Wild-type conidia were less sensitive to the irradiation that albino conidia. In the wild type, carotenoid-enriched conidia were more resistant against the lethal damage than the conidia which contained small amounts of carotenoids. These results suggest that singlet molecular oxygen causes photodynamic lethal damage to N. crassa conidia and that singlet molecular oxygen is quenched by endogenous carotenoids

  19. A comparative study of the processes of generation of singlet oxygen upon irradiation of aqueous preparations on the basis of chlorin e6 and coproporphyrin III

    Science.gov (United States)

    Bagrov, I. V.; Belousova, I. M.; Gorelov, S. I.; Dobrun, M. V.; Kiselev, V. M.; Kislyakov, I. M.; Kris'ko, A. V.; Kris'ko, T. K.

    2017-02-01

    The photosensitizing ability of an agent based on chlorin e6 (Photoditazin), which is used for photodynamic diagnosis and therapy, is compared with that of a new preparation on the basis of coproporphyrin III in the environment of a phosphate buffer and a simulated biological environment (albumin solution). The efficiency of singlet-oxygen production was estimated by EPR spectroscopy and spectroscopy in the UV and visible ranges with the use of "chemical traps" of singlet oxygen. By irradiating drugs with LED emission centered at λmax = 520 nm, we determined the quantum yield of singlet-oxygen production in a buffer solution; the obtained values are 0.60 and 0.37 for chlorine and coproporphyrin, respectively. The steady-state concentration of singlet oxygen upon irradiation of solutions of the studied photosensitizers with concentrations of 12-43 μM and the density of radiation power within the 6-96 W/cm2 region was found to be in the region of 1010-1011 molecules/cm3. It is shown that the introduction into the solution of egg albumin (0.1%) reduces the sensitizing properties of the two drugs by two to three times, while the efficiencies of the preparations with respect to singlet-oxygen production become almost identical (0.19 and 0.17).

  20. Singlet oxygen reactivity in water-rich solvent mixtures

    Directory of Open Access Journals (Sweden)

    Cristina Sousa

    2008-01-01

    Full Text Available The 3-methylindole (3MI oxygenation sensitized by psoralen (PSO has been investigated in 100%, 20% and 5% O2-saturated water/dioxane (H2O/Dx mixtures. The lowering of the ¹O2* chemical rate when water (k chem∆3MI = 1.4 × 109 M-1 s-1 is replaced by deuterated water (k chem∆3MI = 1.9 × 108 M-1 s-1 suggests that hydrogen abstraction is involved in the rate determining step. A high dependence of the chemical rate constant on water concentration in H2O/Dx mixtures was found showing that water molecules are absolutely essential for the success of the 3MI substrate oxidation by ¹O2* in water-rich solvent mixtures.

  1. Singlet oxygen produced by quasi-continuous photo-excitation of hypericin in dimethyl-sulfoxide

    Energy Technology Data Exchange (ETDEWEB)

    Varchola, J.; Želonková, K. [Department of Biophysics, Faculty of Science, P. J. Šafárik University, Jesenná 5, 041 54 Košice (Slovakia); Chorvat Jr, D. [International Laser Centre, Ilkovicova 3, 841 05 Bratislava (Slovakia); Jancura, D. [Department of Biophysics, Faculty of Science, P. J. Šafárik University, Jesenná 5, 041 54 Košice (Slovakia); Center for Interdisciplinary Biosciences, Faculty of Science, P. J. Šafárik University, Jesenná 5, 041 54 Košice (Slovakia); Miskovsky, P. [Department of Biophysics, Faculty of Science, P. J. Šafárik University, Jesenná 5, 041 54 Košice (Slovakia); International Laser Centre, Ilkovicova 3, 841 05 Bratislava (Slovakia); Center for Interdisciplinary Biosciences, Faculty of Science, P. J. Šafárik University, Jesenná 5, 041 54 Košice (Slovakia); and others

    2016-09-15

    Singlet oxygen (O{sub 2}({sup 1}Δ{sub g})) production by photo-excited hypericin (Hyp) dissolved in dimethyl-sulfoxide (DMSO) was studied by means of time-resolved phosphorescence measurements. In order to minimize photo-bleaching, the samples were excited in quasi-continuous mode using long-pulse (35 μs) laser excitation. The measured lifetime of singlet oxygen is τ{sub Δ}=5.5±0.3 μs. This result helps to resolve the discrepancy existing in the literature concerning singlet oxygen lifetime in DMSO. The obtained quantum yield of singlet oxygen photosensitized by Hyp in air-saturated DMSO is Φ{sub Δ}=0.4±0.03. The rate constant for Hyp triplet state depopulation in reaction with ground state molecular oxygen is measured to be k{sub q}=1.6±0.3×10{sup 9} M{sup −1} s{sup −1}.

  2. Pharmaceutical micelles featured with singlet oxygen-responsive cargo release and mitochondrial targeting for enhanced photodynamic therapy

    Science.gov (United States)

    Zhang, Xin; Yan, Qi; Naer Mulatihan, Di; Zhu, Jundong; Fan, Aiping; Wang, Zheng; Zhao, Yanjun

    2018-06-01

    The efficacy of nanoparticulate photodynamic therapy is often compromised by the short life time and limited diffusion radius of singlet oxygen as well as uncontrolled intracellular distribution of photosensitizer. It was hypothesized that rapid photosensitizer release upon nanoparticle internalization and its preferred accumulation in mitochondria would address the above problems. Hence, the aim of this study was to engineer a multifunctional micellar nanosystem featured with singlet oxygen-responsive cargo release and mitochondria-targeting. An imidazole-bearing amphiphilic copolymer was employed as the micelle building block to encapsulate triphenylphosphonium-pyropheophorbide a (TPP-PPa) conjugate or PPa. Upon laser irradiation, the singlet oxygen produced by TPP-PPa/PPa oxidized the imidazole moiety to produce hydrophilic urea, leading to micelle disassembly and rapid cargo release. The co-localization analysis showed that the TPP moiety significantly enhanced the photosensitizer uptake by mitochondria, improved mitochondria depolarization upon irradiation, and hence boosted the cytotoxicity in 4T1 cells. The targeting strategy also dramatically reduced the intracellular ATP concentration as a consequence of mitochondria injury. The mitochondria damage was accompanied with the activation of the apoptosis signals (caspase 3 and caspase 9), whose level was directly correlated to the apoptosis extent. The current work provides a facile and robust means to enhance the efficacy of photodynamic therapy.

  3. Irradiation- and Sensitizer-Dependent Changes in the Lifetime of Intracellular Singlet Oxygen Produced in a Photosensitized Process

    DEFF Research Database (Denmark)

    Silva, Elsa; Pedersen, Brian Wett; Breitenbach, Thomas

    2012-01-01

    Singlet oxygen, O2(a1Δg), was produced upon pulsed-laser irradiation of an intracellular photosensitizer and detected by its 1275 nm O2(a1Δg) →O2(X3Σg-) phosphorescence in time-resolved experiments using (1) individual mammalian cells on the stage of a microscope and (2) suspensions of mammalian...... cells in a 1 cm cuvette. Data were recorded using hydrophilic and, independently, hydrophobic sensitizers. The microscope-based single cell results are consistent with a model in which the behavior of singlet oxygen reflects the environment in which it is produced; nevertheless, the data also indicate...... that a significant fraction of a given singlet oxygen population readily crosses barriers between phase-separated intracellular domains. The singlet oxygen phosphorescence signals reflect the effects of singlet-oxygen-mediated damage on cell components which, at the limit, mean that data were collected from dead...

  4. Singlet oxygen explicit dosimetry to predict local tumor control for HPPH-mediated photodynamic therapy

    Science.gov (United States)

    Penjweini, Rozhin; Kim, Michele M.; Ong, Yi Hong; Zhu, Timothy C.

    2017-02-01

    This preclinical study examines four dosimetric quantities (light fluence, photosensitizer photobleaching ratio, PDT dose, and reacted singlet oxygen ([1O2]rx)) to predict local control rate (LCR) for 2-(1-Hexyloxyethyl)-2-devinyl pyropheophorbide (HPPH)-mediated photodynamic therapy (PDT). Mice bearing radiation-induced fibrosarcoma (RIF) tumors were treated with different in-air fluences (135, 250 and 350 J/cm2) and in-air fluence rates (50, 75 and 150 mW/cm2) at 0.25 mg/kg HPPH and a drug-light interval of 24 hours using a 1 cm diameter collimated laser beam at 665 nm wavelength. A macroscopic model was used to calculate ([1O2]rx)) based on in vivo explicit dosimetry of the initial tissue oxygenation, photosensitizer concentration, and tissue optical properties. PDT dose was defined as a temporal integral of drug concentration and fluence rate (φ) at a 3 mm tumor depth. Light fluence rate was calculated throughout the treatment volume based on Monte-Carlo simulation and measured tissue optical properties. The tumor volume of each mouse was tracked for 30 days after PDT and Kaplan-Meier analyses for LCR were performed based on a tumor volume <=100 mm3, for four dose metrics: fluence, HPPH photobleaching rate, PDT dose, and ([1O2]rx)). The results of this study showed that ([1O2]rx)) is the best dosimetric quantity that can predict tumor response and correlate with LCR.

  5. BODIPY-Au(I): A Photosensitizer for Singlet Oxygen Generation and Photodynamic Therapy.

    Science.gov (United States)

    Üçüncü, Muhammed; Karakuş, Erman; Kurulgan Demirci, Eylem; Sayar, Melike; Dartar, Suay; Emrullahoğlu, Mustafa

    2017-05-19

    Upon complexation with Au(I), a photoinactive BODIPY derivative was transformed into a highly photoactive triplet sensitizer. Along with high efficiency in singlet oxygen generation (Φ Δ = 0.84), the new BODIPY-Au(I) skeleton showed excellent photocytotoxic activity against cancer cell lines (EC 50 = 2.5 nM).

  6. Laser-induced generation of singlet oxygen and its role in the cerebrovascular physiology

    Science.gov (United States)

    Semyachkina-Glushkovskaya, O. V.; Sokolovski, S. G.; Goltsov, A.; Gekaluyk, A. S.; Saranceva, E. I.; Bragina, O. A.; Tuchin, V. V.; Rafailov, E. U.

    2017-09-01

    For over 55 years, laser technology has expanded from laboratory research to widespread fields, for example telecommunication and data storage amongst others. Recently application of lasers in biology and medicine presents itself as one of the emerging areas. In this review, we will outline the recent advances in using lasers for the generation of singlet oxygen, traditionally used to kill tumour cells or induce thrombotic stroke model due to damage vascular effects. Over the last two decade, completely new results on cerebrovascular effects of singlet oxygen generated during photodynamic therapy (PDT) have been shown alongside promising applications for delivery of drugs and nanoparticles into the brain for therapy of brain cancer. Furthermore, a ;gold key; has been found to overcome the limitations of PDT, such as low light penetration and high toxicity of photosensitizers, by direct generation of singlet oxygen using quantum-dot laser diodes emitting in the near infrared (NIR) spectral range. It is our motivation to highlight these pioneering results in this review, to improve understanding of the biological role of singlet oxygen and to provide new perspectives for improving clinical application of laser based therapy in further research.

  7. Impact of photosensitized oxidation and singlet oxygen on degradation of stabilized polymers

    Czech Academy of Sciences Publication Activity Database

    Pospíšil, Jan; Nešpůrek, Stanislav; Pilař, Jan

    2008-01-01

    Roč. 93, č. 9 (2008), s. 1681-1688 ISSN 0141-3910 R&D Projects: GA AV ČR IAA100100622; GA AV ČR KAN400720701; GA AV ČR IAA400500804 Institutional research plan: CEZ:AV0Z40500505 Keywords : photosensitized oxidation * singlet molecular oxygen * oxygenation Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.320, year: 2008

  8. Investigation of the generation of singlet oxygen in ensembles of photoexcited silicon nanocrystals by electron paramagnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Konstantinova, E. A.; Demin, V. A.; Timoshenko, V. Yu.

    2008-01-01

    The generation of singlet oxygen is investigated and its concentration upon photoexcitation of silicon nanocrystals in porous silicon layers is determined using electron paramagnetic resonance spectroscopy. The relaxation times of spin centers, i.e., silicon dangling bonds, in vacuum and in an oxygen atmosphere in the dark and under illumination of the samples are measured for the first time. It is revealed that the spin-lattice relaxation in porous silicon is retarded as compared to that in a single-crystal substrate. From analyzing experimental data, a microscopic model is proposed for interaction of oxygen molecules in the triplet state and spin centers at the surface of silicon nanocrystals. The results obtained have demonstrated that porous silicon holds promise for the use as a photosensitizer of molecular oxygen in biomedical applications

  9. Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer.

    Science.gov (United States)

    Nardi, Giacomo; Manet, Ilse; Monti, Sandra; Miranda, Miguel A; Lhiaubet-Vallet, Virginie

    2014-12-01

    For many biological and biomedical studies, it is essential to detect the production of (1)O2 and quantify its production yield. Among the available methods, detection of the characteristic 1270-nm phosphorescence of singlet oxygen by time-resolved near-infrared (TRNIR) emission constitutes the most direct and unambiguous approach. An alternative indirect method is electron paramagnetic resonance (EPR) in combination with a singlet oxygen probe. This is based on the detection of the TEMPO free radical formed after oxidation of TEMP (2,2,6,6-tetramethylpiperidine) by singlet oxygen. Although the TEMPO/EPR method has been widely employed, it can produce misleading data. This is demonstrated by the present study, in which the quantum yields of singlet oxygen formation obtained by TRNIR emission and by the TEMPO/EPR method are compared for a set of well-known photosensitizers. The results reveal that the TEMPO/EPR method leads to significant overestimation of singlet oxygen yield when the singlet or triplet excited state of the photosensitizer is efficiently quenched by TEMP, acting as electron donor. In such case, generation of the TEMP(+) radical cation, followed by deprotonation and reaction with molecular oxygen, gives rise to an EPR-detectable TEMPO signal that is not associated with singlet oxygen production. This knowledge is essential for an appropriate and error-free application of the TEMPO/EPR method in chemical, biological, and medical studies. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Highly efficient oxidation of amines to imines by singlet oxygen and its application in Ugi-type reactions.

    Science.gov (United States)

    Jiang, Gaoxi; Chen, Jian; Huang, Jie-Sheng; Che, Chi-Ming

    2009-10-15

    A variety of secondary benzylic amines were oxidized to imines in 90% to >99% yields by singlet oxygen generated from oxygen and a porphyrin photosensitizer. On the basis of these reactions, a protocol was developed for oxidative Ugi-type reactions with singlet oxygen as the oxidant. This protocol has been used to synthesize C1- and N-functionalized benzylic amines in up to 96% yields.

  11. Metal bacteriochlorins which act as dual singlet oxygen and superoxide generators.

    Science.gov (United States)

    Fukuzumi, Shunichi; Ohkubo, Kei; Zheng, Xiang; Chen, Yihui; Pandey, Ravindra K; Zhan, Riqiang; Kadish, Karl M

    2008-03-06

    A series of stable free-base, Zn(II) and Pd(II) bacteriochlorins containing a fused six- or five-member diketo- or imide ring have been synthesized as good candidates for photodynamic therapy sensitizers, and their electrochemical, photophysical, and photochemical properties were examined. Photoexcitation of the palladium bacteriochlorin affords the triplet excited state without fluorescence emission, resulting in formation of singlet oxygen with a high quantum yield due to the heavy atom effect of palladium. Electrochemical studies revealed that the zinc bacteriochlorin has the smallest HOMO-LUMO gap of the investigated compounds, and this value is significantly lower than the triplet excited-state energy of the compound in benzonitrile. Such a small HOMO-LUMO gap of the zinc bacteriochlorin enables intermolecular photoinduced electron transfer from the triplet excited state to the ground state to produce both the radical cation and the radical anion. The radical anion thus produced can transfer an electron to molecular oxygen to produce superoxide anion which was detected by electron spin resonance. The same photosensitizer can also act as an efficient singlet oxygen generator. Thus, the same zinc bacteriochlorin can function as a sensitizer with a dual role in that it produces both singlet oxygen and superoxide anion in an aprotic solvent (benzonitrile).

  12. Single Molecule Atomic Force Microscopy Studies of Photosensitized Singlet Oxygen Behavior on a DNA Origami Template

    DEFF Research Database (Denmark)

    Helmig, Sarah Wendelboe; Rotaru, Alexandru; Arian, Dumitru

    2010-01-01

    DNA origami, the folding of a long single-stranded DNA sequence (scaffold strand) by hundreds of short synthetic oligonucleotides (staple strands) into parallel aligned helices, is a highly efficient method to form advanced self-assembled DNA-architectures. Since molecules and various materials can...... be conjugated to each of the short staple strands, the origami method offers a unique possibility of arranging molecules and materials in well-defined positions on a structured surface. Here we combine the action of light with AFM and DNA nanostructures to study the production of singlet oxygen from a single...... photosensitizer molecule conjugated to a selected DNA origami staple strand on an origami structure. We demonstrate a distance-dependent oxidation of organic moieties incorporated in specific positions on DNA origami by singlet oxygen produced from a single photosensitizer located at the center of each origami....

  13. Singlet oxygen generation in a high pressure non-self-sustained electric discharge

    International Nuclear Information System (INIS)

    Hicks, Adam; Norberg, Seth; Shawcross, Paul; Lempert, Walter R; Rich, J William; Adamovich, Igor V

    2005-01-01

    This paper presents results of singlet oxygen generation experiments in a high-pressure, non-self-sustained crossed discharge. The discharge consists of a high-voltage, short pulse duration, high repetition rate pulsed discharge, which produces ionization in the flow, and a low-voltage dc discharge which sustains current in a decaying plasma between the pulses. The sustainer voltage can be independently varied to maximize the energy input into electron impact excitation of singlet delta oxygen (SDO). The results demonstrate operation of a stable and diffuse crossed discharge in O 2 -He mixtures at static pressures of at least up to P 0 = 380 Torr and sustainer discharge powers of at least up to 1200 W, achieved at P 0 = 120 Torr. The reduced electric field in the positive column of the sustainer discharge varies from E/N = 0.3 x 10 -16 to 0.65 X 10 -16 V cm 2 , which is significantly lower than E/N in self-sustained discharges and close to the theoretically predicted optimum value for O 2 (a 1 Δ) excitation. Measurements of visible emission spectra O 2 (b 1 Σ → X 3 Σ) in the discharge afterglow show the O 2 (b 1 Σ) concentration to increase with the sustainer discharge power and to decrease as the O 2 fraction in the flow is increased. Rotational temperatures inferred from these spectra in 10% O 2 -90% He flows at P 0 = 120 Torr and mass flow rates of m-dot = 2.2 are 365-465 K. SDO yield at these conditions, 1.7% to 4.4%, was inferred from the integrated intensity of the (0, 0) band of the O 2 (a 1 Δ → X 3 Σ) infrared emission spectra calibrated using a blackbody source. The yield remains nearly constant in the discharge afterglow, up to at least 15 cm distance from the discharge. Kinetic modelling calculations using a quasi-one-dimensional nonequilibrium pulser-sustainer discharge model coupled with the Boltzmann equation for plasma electrons predict gas temperature rise in the discharge in satisfactory agreement with the experimental measurements

  14. Characterization of photoactivated singlet oxygen damage in single-molecule optical trap experiments.

    Science.gov (United States)

    Landry, Markita P; McCall, Patrick M; Qi, Zhi; Chemla, Yann R

    2009-10-21

    Optical traps or "tweezers" use high-power, near-infrared laser beams to manipulate and apply forces to biological systems, ranging from individual molecules to cells. Although previous studies have established that optical tweezers induce photodamage in live cells, the effects of trap irradiation have yet to be examined in vitro, at the single-molecule level. In this study, we investigate trap-induced damage in a simple system consisting of DNA molecules tethered between optically trapped polystyrene microspheres. We show that exposure to the trapping light affects the lifetime of the tethers, the efficiency with which they can be formed, and their structure. Moreover, we establish that these irreversible effects are caused by oxidative damage from singlet oxygen. This reactive state of molecular oxygen is generated locally by the optical traps in the presence of a sensitizer, which we identify as the trapped polystyrene microspheres. Trap-induced oxidative damage can be reduced greatly by working under anaerobic conditions, using additives that quench singlet oxygen, or trapping microspheres lacking the sensitizers necessary for singlet state photoexcitation. Our findings are relevant to a broad range of trap-based single-molecule experiments-the most common biological application of optical tweezers-and may guide the development of more robust experimental protocols.

  15. Theoretical study of singlet oxygen molecule generation via an exciplex with valence-excited thiophene.

    Science.gov (United States)

    Sumita, Masato; Morihashi, Kenji

    2015-02-05

    Singlet-oxygen [O2((1)Δg)] generation by valence-excited thiophene (TPH) has been investigated using multireference Møller-Plesset second-order perturbation (MRMP2) theory of geometries optimized at the complete active space self-consistent field (CASSCF) theory level. Our results indicate that triplet TPH(1(3)B2) is produced via photoinduced singlet TPH(2(1)A1) because 2(1)A1 TPH shows a large spin-orbit coupling constant with the first triplet excited state (1(3)B2). The relaxed TPH in the 1(3)B2 state can form an exciplex with O2((3)Σg(-)) because this exciplex is energetically more stable than the relaxed TPH. The formation of the TPH(1(3)B2) exciplex with O2((3)Σg(-)) whose total spin multiplicity is triplet (T1 state) increases the likelihood of transition from the T1 state to the singlet ground or first excited singlet state. After the transition, O2((1)Δg) is emitted easily although the favorable product is that from a 2 + 4 cycloaddition reaction.

  16. PHOTOGENERATION OF SINGLET OXYGEN AND FREE RADICALS IN DISSOLVED ORGANIC MATTER ISOLATED FROM THE MISSISSIPPI AND ATCHAFALAYA RIVER PLUMES

    Science.gov (United States)

    The photoreactivity to UV light of ultrafiltered dissolved organic matter (DOM) collected during cruises along salinity transects in the Mississippi and Atchafalaya River plumes was examined by measuring photogenerated free radicals and singlet molecular oxygen (1O2) photosensiti...

  17. BODIPY-pyrene and perylene dyads as heavy atom-free singlet oxygen sensitizers

    KAUST Repository

    Filatov, Mikhail A.

    2018-02-23

    Dyads combining BODIPY as an electron acceptor and pyrene or perylene as electron donor subunits were prepared and studied their photophysical properties studied by steady-state and transient spectroscopy. Depending on the structure of the subunits and polarity of the media, the dyads show either bright fluorescence or photo-induced electron transfer (PeT) in solution. Charge-transfer (CT) states formed as a result of PeT and were found to yield triplet excited states of the BODIPY. In the presence of molecular oxygen, the dyads sensitize singlet oxygen (1O2) with quantum yields of up to 0.75.

  18. BODIPY-pyrene and perylene dyads as heavy atom-free singlet oxygen sensitizers

    KAUST Repository

    Filatov, Mikhail A.; Karuthedath, Safakath; Polestshuk, Pavel M.; Callaghan, Susan; Flanagan, Keith J.; Wiesner, Thomas; Laquai, Fré dé ric; Senge, Mathias O.

    2018-01-01

    Dyads combining BODIPY as an electron acceptor and pyrene or perylene as electron donor subunits were prepared and studied their photophysical properties studied by steady-state and transient spectroscopy. Depending on the structure of the subunits and polarity of the media, the dyads show either bright fluorescence or photo-induced electron transfer (PeT) in solution. Charge-transfer (CT) states formed as a result of PeT and were found to yield triplet excited states of the BODIPY. In the presence of molecular oxygen, the dyads sensitize singlet oxygen (1O2) with quantum yields of up to 0.75.

  19. Singlet oxygen generation during the oxidation of L-tyrosine and L-dopa with mushroom tyrosinase

    Energy Technology Data Exchange (ETDEWEB)

    Miyaji, Akimitsu [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259-G1-14, Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Kohno, Masahiro [Department of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-G1-25 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Inoue, Yoshihiro [Showa Pharmaceutical University, 3-3165 Higashi-tamagawagakuen, Machida, Tokyo 194-8543 (Japan); Baba, Toshihide, E-mail: tbaba@chemenv.titech.ac.jp [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259-G1-14, Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan)

    2016-03-18

    The generation of singlet oxygen during the oxidation of tyrosine and L-dopa using mushroom tyrosinase in a phosphate buffer (pH 7.4), the model of melanin synthesis in melanocytes, was examined. The reaction was performed in the presence of 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP), an acceptor of singlet oxygen and the electron spin resonance (ESR) of the spin adduct, 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy (4-oxo-TEMPO), was measured. An increase in the ESR signal attributable to 4-oxo-TEMPO was observed during the oxidation of tyrosine and L-dopa with tyrosinase, indicating the generation of singlet oxygen. The results suggest that {sup 1}O{sub 2} generation via tyrosinase-catalyzed melanin synthesis occurs in melanocyte. - Highlights: • Generation of singlet oxygen was observed during tyrosinase-catalyzed tyrosine oxidation. • The singlet oxygen generated when tyrosine was converted into dopachrome. • The amount of singlet oxygen is not sufficient for cell toxicity. • It decreased when the hydroxyl radicals and/or superoxide anions were trapped.

  20. Deletion of CGLD1 Impairs PSII and Increases Singlet Oxygen Tolerance of Green Alga Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Jiale Xing

    2017-12-01

    Full Text Available The green alga Chlamydomonas reinhardtii is a key model organism for studying photosynthesis and oxidative stress in unicellular eukaryotes. Using a forward genetics approach, we have identified and characterized a mutant x32, which lacks a predicted protein named CGLD1 (Conserved in Green Lineage and Diatom 1 in GreenCut2, under normal and stress conditions. We show that loss of CGLD1 resulted in minimal photoautotrophic growth and PSII activity in the organism. We observed reduced amount of PSII complex and core subunits in the x32 mutant based on blue-native (BN/PAGE and immunoblot analysis. Moreover, x32 exhibited increased sensitivity to high-light stress and altered tolerance to different reactive oxygenic species (ROS stress treatments, i.e., decreased resistance to H2O2/or tert-Butyl hydroperoxide (t-BOOH and increased tolerance to neutral red (NR and rose bengal (RB that induce the formation of singlet oxygen, respectively. Further analysis via quantitative real-time PCR (qRT-PCR indicated that the increased singlet-oxygen tolerance of x32 was largely correlated with up-regulated gene expression of glutathione-S-transferases (GST. The phenotypical and physiological implications revealed from our experiments highlight the important roles of CGLD1 in maintaining structure and function of PSII as well as in protection of Chlamydomonas under photo-oxidative stress conditions.

  1. Singlet Oxygen-Mediated Oxidation during UVA Radiation Alters the Dynamic of Genomic DNA Replication.

    Directory of Open Access Journals (Sweden)

    Dany Graindorge

    Full Text Available UVA radiation (320-400 nm is a major environmental agent that can exert its deleterious action on living organisms through absorption of the UVA photons by endogenous or exogenous photosensitizers. This leads to the production of reactive oxygen species (ROS, such as singlet oxygen (1O2 and hydrogen peroxide (H2O2, which in turn can modify reversibly or irreversibly biomolecules, such as lipids, proteins and nucleic acids. We have previously reported that UVA-induced ROS strongly inhibit DNA replication in a dose-dependent manner, but independently of the cell cycle checkpoints activation. Here, we report that the production of 1O2 by UVA radiation leads to a transient inhibition of replication fork velocity, a transient decrease in the dNTP pool, a quickly reversible GSH-dependent oxidation of the RRM1 subunit of ribonucleotide reductase and sustained inhibition of origin firing. The time of recovery post irradiation for each of these events can last from few minutes (reduction of oxidized RRM1 to several hours (replication fork velocity and origin firing. The quenching of 1O2 by sodium azide prevents the delay of DNA replication, the decrease in the dNTP pool and the oxidation of RRM1, while inhibition of Chk1 does not prevent the inhibition of origin firing. Although the molecular mechanism remains elusive, our data demonstrate that the dynamic of replication is altered by UVA photosensitization of vitamins via the production of singlet oxygen.

  2. Efficiency factors of singlet oxygen generation from core-modified expanded porphyrin: tetrathiarubyrin in ethanol

    CERN Document Server

    Ha, J H; Kim, Y R; Jung, G Y; Lee, Y H; Shin, K

    2001-01-01

    The photophysical properties and the singlet oxygen generation efficiency of tetrathiarubyrin have been investigated to elucidate the possibility of its use as a photodynamic therapy (PDT) photosensitizer by steady-state and time-resolved spectroscopic methods. The observed photophysical properties were affected by various molecular aspects, such as extended pi conjugation, structural distortion, and internal heavy atom. The steady-state electronic absorption spectrum was red-shifted due to the extended pi-conjugation, and the spin orbital coupling was enhanced by the structural distortion and the internal heavy atom effect. As a result of the enhanced spin orbital coupling, the triplet quantum yield increased to 0.90 +- 0.10 and the triplet state lifetime was shortened to 7.0 +- 1.2 mu s. Since the triplet state decays at a relatively faster rate, the efficiency of the oxygen quenching of the triplet state decreases. The singlet oxygen quantum yield was estimated to be 0.52 +- 0.02, which is somewhat lower t...

  3. Singlet Oxygen-Mediated Oxidation during UVA Radiation Alters the Dynamic of Genomic DNA Replication

    Science.gov (United States)

    Graindorge, Dany; Martineau, Sylvain; Machon, Christelle; Arnoux, Philippe; Guitton, Jérôme; Francesconi, Stefania; Frochot, Céline; Sage, Evelyne; Girard, Pierre-Marie

    2015-01-01

    UVA radiation (320–400 nm) is a major environmental agent that can exert its deleterious action on living organisms through absorption of the UVA photons by endogenous or exogenous photosensitizers. This leads to the production of reactive oxygen species (ROS), such as singlet oxygen (1O2) and hydrogen peroxide (H2O2), which in turn can modify reversibly or irreversibly biomolecules, such as lipids, proteins and nucleic acids. We have previously reported that UVA-induced ROS strongly inhibit DNA replication in a dose-dependent manner, but independently of the cell cycle checkpoints activation. Here, we report that the production of 1O2 by UVA radiation leads to a transient inhibition of replication fork velocity, a transient decrease in the dNTP pool, a quickly reversible GSH-dependent oxidation of the RRM1 subunit of ribonucleotide reductase and sustained inhibition of origin firing. The time of recovery post irradiation for each of these events can last from few minutes (reduction of oxidized RRM1) to several hours (replication fork velocity and origin firing). The quenching of 1O2 by sodium azide prevents the delay of DNA replication, the decrease in the dNTP pool and the oxidation of RRM1, while inhibition of Chk1 does not prevent the inhibition of origin firing. Although the molecular mechanism remains elusive, our data demonstrate that the dynamic of replication is altered by UVA photosensitization of vitamins via the production of singlet oxygen. PMID:26485711

  4. The participation of singlet oxygen in a photocitotoxicity of extract from amazon plant to cancer cells

    Science.gov (United States)

    Tcibulnikova, Anna V.; Degterev, Igor A.; Bryukhanov, Valery V.; Roberto, Mantuanelly M.; Campos Pereira, F. D.; Marin-Morales, M. A.; Slezhkin, Vasily A.; Samusev, Ilya G.

    2018-01-01

    We have been searching for new photosensitizers (PS) for photodynamic therapy (PDT) of cancer based on extracts from Amazonian plants since 2009. In this paper, we demonstrate that, under certain conditions, the extract from fruits of the Amazonian palm Euterpe oleraceae (popular name Açaí) can serve as a PS for PDT treatment of murine breast cancer cells (4T1 cell line). We have been first to show directly that the photodynamic effect of plant PS is due to singlet oxygen.

  5. Layered Double Hydroxides with Intercalated Porphyrins as Photofunctional Materials: Subtle Structural Changes Modify Singlet Oxygen Production

    Czech Academy of Sciences Publication Activity Database

    Lang, Kamil; Bezdička, Petr; Bourdelande, J.L.; Hernando, J.; Jirka, Ivan; Káfuňková, Eva; Kubát, Pavel; Mosinger, Jiří; Wagnerová, Dana Marie

    2007-01-01

    Roč. 19, č. 15 (2007), s. 3822-3829 ISSN 0897-4756 R&D Projects: GA ČR(CZ) GA203/06/1244; GA ČR GA203/07/1424; GA AV ČR KAN100500651 Grant - others:MESS(ES) CTQ2006-01040 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z40400503 Keywords : singlet oxygen Subject RIV: CA - Inorganic Chemistry Impact factor: 4.883, year: 2007

  6. UVA Photoirradiation of Oxygenated Benz[a]anthracene and 3-Methylcholanthene - Generation of Singlet Oxygen and Induction of Lipid Peroxidation

    Directory of Open Access Journals (Sweden)

    Diógenes Herreño Sáenz

    2008-03-01

    Full Text Available Polycyclic aromatic hydrocarbons (PAHs are widespread genotoxic environmental pollutants and potentially pose a health risk to humans. Although the biological and toxicological activities, including metabolism, mutagenicity, and carcinogenicity, of PAHs have been thoroughly studied, their phototoxicity and photo-induced biological activity have not been well examined. We have long been interested in phototoxicity of PAHs and their derivatives induced by irradiation with UV light. In this paper we report the photoirradiation of a series of oxygenated benz[a]anthracene (BA and 3-methylcholanthene (3-MC by UVA light in the presence of a lipid, methyl linoleate. The studied PAHs include 2-hydroxy-BA (2-OH-BA, 3-hydroxy-BA (3-OH-BA, 5-hydroxymethyl-BA (5-CH2OH-BA, 7-hydroxymethyl-BA (7-CH2OH-BA, 12-hydroxymethyl-BA (12-CH2OH-BA, 7-hydroxymethyl-12-methyl-BA (7-CH2OH-12-MBA, 5-formyl-BA (5-CHO-BA, BA 5,6-cis-dihydrodiol (BA 5,6-cis-diol, 1-hydroxy-3- methylcholanthene (1-OH-3-MC, 1-keto-3-methylcholanthene (1-keto-3-MC, and 3-MC 1,2-diol. The results indicate that upon photoirradiation by UVA at 7 and 21 J/cm2, respectively all these compounds induced lipid peroxidation and exhibited a relationship between the dose of the light and the level of lipid peroxidation induced. To determine whether or not photoirradiation of these compounds by UVA light produces ROS, an ESR spin-trap technique was employed to provide direct evidence. Photoirradiation of 3-keto-3-MC by UVA (at 389 nm in the presence of 2,2,6,6-tetramethylpiperidine (TEMP, a specific probe for singlet oxygen, resulted in the formation of TEMPO, indicating that singlet oxygen was generated. These overall results suggest that UVA photoirradiation of oxygenated BA and 3-methylcholanthrene generates singlet oxygen, one of the reactive oxygen species (ROS, which induce lipid peroxidation.

  7. Continuous-flow oxidative cyanation of primary and secondary amines using singlet oxygen.

    Science.gov (United States)

    Ushakov, Dmitry B; Gilmore, Kerry; Kopetzki, Daniel; McQuade, D Tyler; Seeberger, Peter H

    2014-01-07

    Primary and secondary amines can be rapidly and quantitatively oxidized to the corresponding imines by singlet oxygen. This reactive form of oxygen was produced using a variable-temperature continuous-flow LED-photoreactor with a catalytic amount of tetraphenylporphyrin as the sensitizer. α-Aminonitriles were obtained in good to excellent yields when trimethylsilyl cyanide served as an in situ imine trap. At 25°C, primary amines were found to undergo oxidative coupling prior to cyanide addition and yielded secondary α-aminonitriles. Primary α-aminonitriles were synthesized from the corresponding primary amines for the first time, by an oxidative Strecker reaction at -50 °C. This atom-economic and protecting-group-free pathway provides a route to racemic amino acids, which was exemplified by the synthesis of tert-leucine hydrochloride from neopentylamine. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Ultrasound-assisted interaction between chlorin-e6 and human serum albumin: pH dependence, singlet oxygen production, and formulation effect

    Science.gov (United States)

    Mocanu, Mihaela N.; Yan, Fei

    2018-02-01

    The interaction between chlorin e6 (Ce6) and human serum albumin (HSA) in the presence and absence of ultrasound have been investigated by ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy. Ce6 is found to bind strongly to HSA at or near physiological pH conditions, but the strength of the binding is significantly weakened at lower pHs. The intrinsic fluorescence of HSA is incrementally quenched with increasing concentration of Ce6, and the quenching is enhanced after exposure to high-frequency ultrasound. Our experimental results suggest that Ce6-induced sonodynamic oxidation of HSA is mainly mediated by singlet oxygen. The formulation of Ce6 by high molecular weight polyvinylpyrrolidone (PVP) increased its stability in aqueous solutions and its quantum yield of singlet oxygen under ultrasound irradiation.

  9. Influence of clay minerals on curcumin properties: Stability and singlet oxygen generation

    Science.gov (United States)

    Gonçalves, Joyce L. S.; Valandro, Silvano R.; Poli, Alessandra L.; Schmitt, Carla C.

    2017-09-01

    Curcumin (CUR) has showed promising photophysical properties regarding to biological and chemical sciences. However, the main barrier for those applications are their low solubility and stability in aqueous solution. The effects of two different clay minerals, the montmorillonite (SWy-2) and the Laponite RD (Lap) nanoclay, on the stabilization of Curcumin were investigated. Their effects were compared with two well-established environments (acidic and neutral aqueous media). CUR/clay hybrids were prepared using a simple and fast method, where CUR solution was added into clay suspensions, to obtain well dispersed hybrids in water. The degradation process of CUR and CUR/clays hybrids was investigated using UV-Vis spectroscopic. For both studied hybrids, the CUR degradation process was suppressed by the presence of the clay particles. Furthermore, the Lap showed a great stabilization effect than SWy-2. This behavior was due to the smaller particle size and higher exfoliation ability of Lap, providing a large surface for CUR adsorption compared to SWy-2. The degradation process of CUR solutions and CUR/clay hybrids was also studied in the presence of light. CUR photodegradation process was faster not only in the aqueous solution but also in the clay suspension compared to those studied in the dark. The presence of clay particles accelerated the photodegradation of CUR due to the products formation in the reactions between CUR and oxygen radicals. Our results showed that the singlet oxygen quantum yield (ΦΔ) of CUR were about 59% higher in the clay suspensions than CUR in aqueous solution. Therefore, the formation of CUR/clay hybrids, in particularly with Lap, suppressed the degradation in absence light of CUR and increased the singlet oxygen generation, which makes this hybrids of CUR/clay a promising material to enlarge the application of CUR in the biological sciences.

  10. Time-resolved EPR study of singlet oxygen in the gas phase.

    Science.gov (United States)

    Ruzzi, Marco; Sartori, Elena; Moscatelli, Alberto; Khudyakov, Igor V; Turro, Nicholas J

    2013-06-27

    X-band EPR spectra of singlet O2((1)Δg) and triplet O2((3)Σg(-)) were observed in the gas phase under low molecular-oxygen pressures PO2 = 0.175-0.625 Torr, T = 293-323 K. O2((1)Δg) was produced by quenching of photogenerated triplet sensitizers naphthalene C8H10, perdeuterated naphthalene, and perfluoronaphthalene in the gas phase. The EPR spectrum of O2((1)Δg) was also observed under microwave discharge. Integrated intensities and line widths of individual components of the EPR spectrum of O2((3)Σg(-)) were used as internal standards for estimating the concentration of O2 species and PO2 in the EPR cavity. Time-resolved (TR) EPR experiments of C8H10 were the main focus of this Article. Pulsed irradiation of C8H10 in the presence of O2((3)Σg(-)) allowed us to determine the kinetics of formation and decay for each of the four components of the O2((1)Δg) EPR signal, which lasted for only a few seconds. We found that the kinetics of EPR-component decay fit nicely to a biexponential kinetics law. The TR EPR 2D spectrum of the third component of the O2((1)Δg) EPR spectrum was examined in experiments using C8H10. This spectrum vividly presents the time evolution of an EPR component. The largest EPR signal and the longest lifetime of O2((1)Δg), τ = 0.4 s, were observed at medium pressure PO2 = 0.4 Torr, T = 293 K. The mechanism of O2((1)Δg) decay in the presence of photosensitizers is discussed. EPR spectra of O2((1)Δg) evidence that the spin-rotational states of O2((1)Δg) are populated according to Boltzmann distribution in the studied time range of 10-100 ms. We believe that this is the first report dealing with the dependence of O2((1)Δg) EPR line width on PO2 and T.

  11. Light absorption and the photoformation of hydroxyl radical and singlet oxygen in fog waters

    Science.gov (United States)

    Kaur, R.; Anastasio, C.

    2017-09-01

    The atmospheric aqueous-phase is a rich medium for chemical transformations of organic compounds, in part via photooxidants generated within the drops. Here we measure light absorption, photoformation rates and steady-state concentrations of two photooxidants - hydroxyl radical (•OH) and singlet molecular oxygen (1O2*) - in 8 illuminated fog waters from Davis, California and Baton Rouge, Louisiana. Mass absorption coefficients for dissolved organic compounds (MACDOC) in the samples are large, with typical values of 10,000-15,000 cm2 g-C-1 at 300 nm, and absorption extends to wavelengths as long as 450-600 nm. While nitrite and nitrate together account for an average of only 1% of light absorption, they account for an average of 70% of •OH photoproduction. Mean •OH photoproduction rates in fogs at the two locations are very similar, with an overall mean of 1.2 (±0.7) μM h-1 under Davis winter sunlight. The mean (±1σ) lifetime of •OH is 1.6 (±0.6) μs, likely controlled by dissolved organic compounds. Including calculated gas-to-drop partitioning of •OH, the average aqueous concentration of •OH is approximately 2 × 10-15 M (midday during Davis winter), with aqueous reactions providing approximately one-third of the hydroxyl radical source. At this concentration, calculated lifetimes of aqueous organics are on the order of 10 h for compounds with •OH rate constants of 1 × 1010 M-1 s-1 or higher (e.g., substituted phenols such as syringol (6.4 h) and guaiacol (8.4 h)), and on the order of 100 h for compounds with rate constants near 1 × 109 M-1 s-1 (e.g., isoprene oxidation products such as glyoxal (152 h), glyoxylic acid (58 h), and pyruvic acid (239 h)). Steady-state concentrations of 1O2* are approximately 100 times higher than those of •OH, in the range of (0.1-3.0) × 10-13 M. Since 1O2* is a more selective oxidant than •OH, it will only react appreciably with electron-rich species such as dimethyl furan (lifetime of 2.0 h) and

  12. Stability of O/W Emulsion with Synthetic Perfumes Oxidized by Singlet Oxygen

    Directory of Open Access Journals (Sweden)

    Naoki Watabe

    2013-01-01

    Full Text Available We prepared O/W emulsion composed of a synthetic perfume, n-dodecane, protoporphyrin IX disodium salt (PpIX-2Na, sodium dodecyl sulfate, and water and investigated oxidative decomposition of the synthetic perfume in the emulsion and change in the stability of the emulsion by singlet oxygen (1O2 generated by photosensitization of PpIX-2Na. We used eugenol, linalool, benzyl acetate, α-ionone, α-hexylcinnamaldehyde, and d-limonene as a synthetic perfume. The stability of the O/W emulation including eugenol and linalool significantly decreased with increasing light irradiation time. The decrease in the emulsion stability may be attributable to oxidative decomposition of eugenol and linalool by 1O2 and enlargement of the oil droplet size.

  13. Factors influencing the regioselectivity of the oxidation of asymmetric secondary amines with singlet oxygen.

    Science.gov (United States)

    Ushakov, Dmitry B; Plutschack, Matthew B; Gilmore, Kerry; Seeberger, Peter H

    2015-04-20

    Aerobic amine oxidation is an attractive and elegant process for the α functionalization of amines. However, there are still several mechanistic uncertainties, particularly the factors governing the regioselectivity of the oxidation of asymmetric secondary amines and the oxidation rates of mixed primary amines. Herein, it is reported that singlet-oxygen-mediated oxidation of 1° and 2° amines is sensitive to the strength of the α-C-H bond and steric factors. Estimation of the relative bond dissociation energy by natural bond order analysis or by means of one-bond C-H coupling constants allowed the regioselectivity of secondary amine oxidations to be explained and predicted. In addition, the findings were utilized to synthesize highly regioselective substrates and perform selective amine cross-couplings to produce imines. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Singlet oxygen explicit dosimetry to predict long-term local tumor control for Photofrin-mediated photodynamic therapy

    Science.gov (United States)

    Penjweini, Rozhin; Kim, Michele M.; Ong, Yi Hong; Zhu, Timothy C.

    2017-02-01

    Although photodynamic therapy (PDT) is an established modality for the treatment of cancer, current dosimetric quantities do not account for the variations in PDT oxygen consumption for different fluence rates (φ). In this study we examine the efficacy of reacted singlet oxygen concentration ([1O2]rx) to predict long-term local control rate (LCR) for Photofrin-mediated PDT. Radiation-induced fibrosarcoma (RIF) tumors in the right shoulders of female C3H mice are treated with different in-air fluences of 225-540 J/cm2 and in-air fluence rate (φair) of 50 and 75 mW/cm2 at 5 mg/kg Photofrin and a drug-light interval of 24 hours using a 1 cm diameter collimated laser beam at 630 nm wavelength. [1O2]rx is calculated by using a macroscopic model based on explicit dosimetry of Photofrin concentration, tissue optical properties, tissue oxygenation and blood flow changes during PDT. The tumor volume of each mouse is tracked for 90 days after PDT and Kaplan-Meier analyses for LCR are performed based on a tumor volume defined as a temporal integral of photosensitizer concentration and Φ at a 3 mm tumor depth. φ is calculated throughout the treatment volume based on Monte-Carlo simulation and measured tissue optical properties. Our preliminary studies show that [1O2]rx is the best dosimetric quantity that can predict tumor response and correlate with LCR. Moreover, [1O2]rx calculated using the blood flow changes was in agreement with [1O2]rx calculated based on the actual tissue oxygenation.

  15. Gold nanoring-enhanced generation of singlet oxygen: an intricate correlation with surface plasmon resonance and polyelectrolyte bilayers

    Czech Academy of Sciences Publication Activity Database

    Hu, Y.; Kaňka, Jiří; Liu, K.; Yang, Y.; Wang, H.; Du, H.

    2016-01-01

    Roč. 6, č. 106 (2016), s. 104819-104826 ISSN 2046-2069 R&D Projects: GA ČR(CZ) GBP205/12/G118 Institutional support: RVO:67985882 Keywords : Singlet oxygen * Fluorescence * Gold nanorings Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.108, year: 2016

  16. Irradiation- and Sensitizer-Dependent Changes in the Lifetime of Intracellular Singlet Oxygen Produced in a Photosensitized Process

    DEFF Research Database (Denmark)

    Silva, Elsa; Pedersen, Brian Wett; Breitenbach, Thomas

    2012-01-01

    Singlet oxygen, O2(a1Δg), was produced upon pulsed-laser irradiation of an intracellular photosensitizer and detected by its 1275 nm O2(a1Δg) →O2(X3Σg-) phosphorescence in time-resolved experiments using (1) individual mammalian cells on the stage of a microscope and (2) suspensions of mammalian...

  17. Fluorescent proteins as singlet oxygen photosensitizers: mechanistic studies in photodynamic inactivation of bacteria

    Science.gov (United States)

    Ruiz-González, Rubén.; White, John H.; Cortajarena, Aitziber L.; Agut, Montserrat; Nonell, Santi; Flors, Cristina

    2013-02-01

    Antimicrobial photodynamic therapy (aPDT) combines a photosensitizer, light and oxygen to produce reactive oxygen species (ROS), mainly singlet oxygen (1O2), to photo-oxidize important biomolecules and induce cell death. aPDT is a promising alternative to standard antimicrobial strategies, but its mechanisms of action are not well understood. One of the reasons for that is the lack of control of the photosensitizing drugs location. Here we report the use of geneticallyencoded fluorescent proteins that are also 1O2 photosensitizers to address the latter issue. First, we have chosen the red fluorescent protein TagRFP as a photosensitizer, which unlike other fluorescent proteins such as KillerRed, is able to produce 1O2 but not other ROS. TagRFP photosensitizes 1O2 with a small, but not negligible, quantum yield. In addition, we have used miniSOG, a more efficient 1O2 photosensitizing fluorescent flavoprotein that has been recently engineered from phototropin 2. We have genetically incorporated these two photosensitizers into the cytosol of E. coli and demonstrated that intracellular 1O2 is sufficient to kill bacteria. Additional assays have provided further insight into the mechanism of cell death. Photodamage seems to occur primarily in the inner membrane, and extends to the outer membrane if the photosensitizer's efficiency is high enough. These observations are markedly different to those reported for external photosensitizers, suggesting that the site where 1O2 is primarily generated proves crucial for inflicting different types of cell damage.

  18. Physics and engineering of singlet delta oxygen production in low-temperature plasma

    International Nuclear Information System (INIS)

    Ionin, A A; Kochetov, I V; Napartovich, A P; Yuryshev, N N

    2007-01-01

    An overview is presented of experimental and theoretical research in the field of physics and engineering of singlet delta oxygen (SDO) production in low-temperature plasma of various electric discharges. Attention is paid mainly to the SDO production with SDO yield adequate for the development of an electric discharge oxygen-iodine laser (DOIL). The review comprises a historical sketch describing the main experimental results on SDO physics in low-temperature plasma obtained since the first detection of SDO in electric discharge in the 1950s and the first attempt to launch a DOIL in the 1970s up to the mid-1980s when several research groups started their activity aimed at DOIL development, stimulated by success in the development of a chemical oxygen-iodine laser (COIL). A detailed analysis of theoretical and experimental research on SDO production in electric discharge from the mid-1980s to the present, when the first DOIL has been launched, is given. Different kinetic models of oxygen low-temperature plasma are compared with the model developed by the authors. The latter comprises electron kinetics based on the accompanying solution of the electron Boltzmann equation, plasma chemistry including reactions of excited molecules and numerous ion-molecular reactions, thermal energy balance and electric circuit equation. The experimental part of the overview is focused on the experimental methods of SDO detection including experiments on the measurements of the Einstein coefficient for SDO transition a 1 Δ g - X 3 Σ g - and experimental procedures of SDO production in self-sustained and non-self-sustained discharges and analysis of different plasma-chemical processes occurring in oxygen low-temperature plasma which brings limitation to the maximum SDO yield and to the lifetime of the SDO in an electric discharge and its afterglow. Quite recently obtained results on gain and output characteristics of DOIL and some projects aimed at the development of high-power DOIL

  19. Singlet oxygen explicit dosimetry to predict long-term local tumor control for BPD-mediated photodynamic therapy

    Science.gov (United States)

    Kim, Michele M.; Penjweini, Rozhin; Ong, Yi Hong; Zhu, Timothy C.

    2017-02-01

    Photodynamic therapy (PDT) is a well-established treatment modality for cancer and other malignant diseases; however, quantities such as light fluence, photosensitizer photobleaching rate, and PDT dose do not fully account for all of the dynamic interactions between the key components involved. In particular, fluence rate (Φ) effects are not accounted for, which has a large effect on the oxygen consumption rate. In this preclinical study, reacted singlet oxygen [1O2]rx was investigated as a dosimetric quantity for PDT outcome. The ability of [1O2]rx to predict the long-term local tumor control rate (LCR) for BPD-mediated PDT was examined. Mice bearing radioactivelyinduced fibrosarcoma (RIF) tumors were treated with different in-air fluences (250, 300, and 350 J/cm2) and in-air ϕ (75, 100, and150 mW/cm2) with a BPD dose of 1 mg/kg and a drug-light interval of 3 hours. Treatment was delivered with a collimated laser beam of 1 cm diameter at 690 nm. Explicit dosimetry of initial tissue oxygen concentration, tissue optical properties, and BPD concentration was used to calculate [1O2]rx. Φ was calculated for the treatment volume based on Monte-Carlo simulations and measured tissue optical properties. Kaplan-Meier analyses for LCR were done for an endpoint of tumor volume defined as the product of the timeintegral of photosensitizer concentration and Φ at a 3 mm tumor depth. Preliminary studies show that [1O2]rx better correlates with LCR and is an effective dosimetric quantity that can predict treatment outcome.

  20. Oxygen Concentration Inside a Functioning Photosynthetic Cell

    OpenAIRE

    Kihara, Shigeharu; Hartzler, Daniel A.; Savikhin, Sergei

    2014-01-01

    The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic...

  1. A Possible Role for Singlet Oxygen in the Degradation of Various Antioxidants. A Meta-Analysis and Review of Literature Data

    Directory of Open Access Journals (Sweden)

    Athinoula L. Petrou

    2018-02-01

    Full Text Available The thermodynamic parameters Eact, ΔH≠, ΔS≠, and ΔG≠ for various processes involving antioxidants were calculated using literature kinetic data (k, T. The ΔG≠ values of the antioxidants’ processes vary in the range 91.27–116.46 kJmol−1 at 310 K. The similarity of the ΔG≠ values (for all of the antioxidants studied is supported to be an indication that a common mechanism in the above antioxidant processes may be taking place. A value of about 10–30 kJmol−1 is the activation energy for the diffusion of reactants depending on the reaction and the medium. The energy 92 kJmol−1 is needed for the excitation of O2 from the ground to the first excited state (1Δg, singlet oxygen. We suggest the same role of the oxidative stress and specifically of singlet oxygen to the processes of antioxidants as in the processes of proteinaceous diseases. We therefore suggest a competition between the various antioxidants and the proteins of proteinaceous diseases in capturing singlet oxygen’s empty π* orbital. The concentration of the antioxidants could be a crucial factor for the competition. Also, the structures of the antioxidant molecules play a significant role since the various structures have a different number of regions of high electron density.

  2. High-sensitivity imaging method of singlet oxygen and superoxide anion in photodynamic and sonodynamic actions

    Science.gov (United States)

    Xing, Da; He, Yonghong; Hao, Min; Chen, Qun

    2004-07-01

    A novel method of photodynamic diagnosis (PDD) of cancer mediated by chemiluminescence (CL) probe is presented. The mechanism for photodynamic therapy (PDT) involves reactive oxygen species (ROS), such as singlet oxygen (1O2) and superoxide (O2-), generated by during the photochemical process. Both 1O2 and O2- can react with Cypridina luciferin analogue (FCLA), a highly selective CL probe for detecting the ROS. Chemiluminescence from the reaction of FCLA with the ROS, at about 530 nm, was detected by a highly sensitive ICCD system. The CL was markedly inhibited by the addition of 10 mmol/L sodium azide (NaN3) in a sample solution. Similar phenomena, with lesser extents of changes, were observed at the additions of 10 μmol/L superoxide dismutase (SOD), 10 mmol/L mannitol, and 100 μg/mL catalase, respectively. This indicates that the detected CL signals were mainly from ROS generated during the photosensitization reactions. Also, the chemiluminescence method was used to detect the ROS during sonodynamic action, both in vitro and in vivo. ROS formation during sonosensitizations of HpD and ATX-70 were detected using our newly-developed imaging technique, in real time, on tumor bearing animals. This method can provide a new means in clinics for tumor diagnosis.

  3. Activation of transcription factor AP-2 mediates UVA radiation- and singlet oxygen-induced expression of the human intercellular adhesion molecule 1 gene

    International Nuclear Information System (INIS)

    Grether-Beck, S.; Olaizola-Horn, S.; Schmitt, H.; Grewe, M.

    1996-01-01

    UVA radiation is the major component of the UV solar spectrum that reaches the earth, and the therapeutic application of UVA radiation is increasing in medicine. Analysis of the cellular effects of UVA radiation has revealed that exposure of human cells to UVA radiation at physiological doses leads to increased gene expression and that this UVA response is primarily mediated through the generation of singlet oxygen. In this study, the mechanisms by which UVA radiation induces transcriptional activation of the human intercellular adhesion molecule 1 (ICAM-1) were examined. UVA radiation was capable of inducing activation of the human ICAM-1 promoter and increasing OCAM-1 mRNA and protein expression. These UVA radiation effects were inhibited by singlet oxygen quenchers, augmented by enhancement of singlet oxygen life-time, and mimicked in unirradiated cells by a singlet oxygen-generating system. UVA radiation as well as singlet oxygen-induced ICAM-1 promoter activation required activation of the transcription factor AP-2. Accordingly, both stimuli activated AP-2, and deletion of the putative AP-2-binding site abrogated ICAM-1 promoter activation in this system. This study identified the AP-2 site as the UVA radiation- and singlet oxygen-responsive element of the human ICAM-1 gene. The capacity of UVA radiation and/or singlet oxygen to induce human gene expression through activation of AP-2 indicates a previously unrecognized role of this transcription factor in the mammalian stress response. 38 refs., 3 figs., 3 tabs

  4. A Singlet Oxygen Photogeneration and Luminescence Study of Unsymmetrically Substituted Mesoporphyrinic Compounds

    Directory of Open Access Journals (Sweden)

    Anabela Sousa Oliveira

    2009-01-01

    Full Text Available This paper deals with a series of new unsymmetrically substituted mesoporphyrins: 5-(2-hydroxyphenyl-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPOHO, 5-(3-hydroxyphenyl-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPOHM, 5-(4-hydroxyphenyl-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPOHP, 5-(2-hydroxyphenyl-10,15,20-tris-butyl-21,23-H-porphyrin (TBPOHO, and their parent nonsubstituted compounds, respectively, 5,10,15,20-tetrakis-phenyl-21,23-H-porphyrin (TPP and 5,10,15,20-tetrakis-butyl-21,23-H-porphyrin (TBP. Several photophysical studies were carried out to access the influence of the unsymmetrical substitution at the porphyrinic macrocycle on porthyrin's photophysical properties, especially porthyrin's efficiency as singlet oxygen sensitizers. The quantum yields of singlet oxygen generation were determined in benzene (ΦΔ(TPP = 0.66 ± 0.05; ΦΔ(TPPOHO = 0.69 ± 0.04; ΦΔ(TPPOHM = 0.62 ± 0.04; ΦΔ(TPPOHP = 0.73 ± 0.03; ΦΔ(TBP = 0.76 ± 0.03; ΦΔ(TBPOHO = 0.73 ± 0.02 using the 5,10,15,20-tetraphenyl-21,23-H-porphine (ΦΔ(TPP = 0.66 and Phenazine (ΦΔ(Phz = 0.83 as reference compounds. Their fluorescence quantum yields were found to be (Φf(TPPOHO = 0.10 ± 0.04; Φf(TPPOHM = 0.09 ± 0.03; Φf(TPPOHP = 0.13 ± 0.02; Φf(TBP = 0.08 ± 0.03 and Φf(TBPOHO = 0.08 ± 0.02 using 5,10,15,20-tetraphenyl-21,23-H-porphine as reference Φf(TPP = 0.13. Singlet state lifetimes were also determined in the same solvent. All the porphyrins presented very similar fluorescence lifetimes (mean values of τS (with O2, air equilibrated = 9.6 ± 0.3 nanoseconds and (without O2, argon purged = 10.1 ± 0.6 nanoseconds, resp.. The phosphorescence emission was found to be negligible for this series of unsymmetrically substituted mesoporphyrins, but an E-type, thermally activated, delayed fluorescence process was proved to occur at room temperature.

  5. The effect of gold nanoparticles on exchange processes in collision complexes of triplet and singlet oxygen molecules with excited eosin molecules

    Science.gov (United States)

    Bryukhanov, V. V.; Minaev, B. M.; Tsibul'nikova, A. V.; Slezhkin, V. A.

    2015-07-01

    We have studied exchange processes in contact complexes of triplet eosin molecules with oxygen molecules in the triplet (3Σ{/g -}) and singlet (1Δ g ) states in thin polyvinylbutyral films in the presence of gold nanoparticles. Upon resonant excitation of surface plasmons in gold nanoparticles into the absorption band of eosin molecules-singlet oxygen sensitizers-we have obtained an increase in the intensity of the delayed fluorescence and an increase in the lifetime of the dye with simultaneous quenching of the luminescence of singlet oxygen. The kinetics of the delayed fluorescence of the dye as a result of singlet-triplet annihilation of triplet eosin molecules with singlet oxygen molecules has been investigated. To compare theoretical and experimental data, we have numerically simulated energy transfer processes. Rate constants of energy transfer and of singlet-triplet annihilation, as well as quenching constants of triplet states of the dye by molecular oxygen, have been calculated. Luminescence quantum yield 1Δ g of polyvinylbutyral has been estimated. We have analyzed quantum-chemically electronic mechanisms of singlet-triplet annihilation of oxygen and eosin.

  6. Formation of singlet oxygen by decomposition of protein hydroperoxide in photosystem II.

    Directory of Open Access Journals (Sweden)

    Vinay Pathak

    Full Text Available Singlet oxygen (1O2 is formed by triplet-triplet energy transfer from triplet chlorophyll to O2 via Type II photosensitization reaction in photosystem II (PSII. Formation of triplet chlorophyll is associated with the change in spin state of the excited electron and recombination of triplet radical pair in the PSII antenna complex and reaction center, respectively. Here, we have provided evidence for the formation of 1O2 by decomposition of protein hydroperoxide in PSII membranes deprived of Mn4O5Ca complex. Protein hydroperoxide is formed by protein oxidation initiated by highly oxidizing chlorophyll cation radical and hydroxyl radical formed by Type I photosensitization reaction. Under highly oxidizing conditions, protein hydroperoxide is oxidized to protein peroxyl radical which either cyclizes to dioxetane or recombines with another protein peroxyl radical to tetroxide. These highly unstable intermediates decompose to triplet carbonyls which transfer energy to O2 forming 1O2. Data presented in this study show for the first time that 1O2 is formed by decomposition of protein hydroperoxide in PSII membranes deprived of Mn4O5Ca complex.

  7. Singlet Oxygen Production by Illuminated Road Dust and Winter Street Sweepings

    Science.gov (United States)

    Schneider, S.; Gan, L.; Gao, S.; Hoy, K. S.; Kwasny, J. R.; Styler, S. A.

    2017-12-01

    Road dust is an important urban source of primary particulate matter, especially in cities where sand and other traction materials are applied to roadways in winter. Although the composition and detrimental health effects of road dust are reasonably well characterized, little is currently known regarding its chemical behaviour. Motivated by our previous work, in which we showed that road dust is a photochemical source of singlet oxygen (1O2), we investigated 1O2 production by bulk winter street sweepings and by road dust collected in a variety of urban, industrial, and suburban locations in both autumn and spring. In all cases, the production of 1O2 by road dust was greater than that by Arizona test dust and desert-sourced dust, which highlights the unique photochemical environment afforded by this substrate. Mechanistically, we observed correlations between 1O2 production and the UV absorbance properties of dust extracts, which suggests the involvement of chromophoric dissolved organic matter in the observed photochemistry. Taken together, this work provides evidence that road dust-mediated photochemistry may influence the environmental lifetime of pollutants that react via 1O2-mediated pathways, including polycyclic aromatic hydrocarbons.

  8. Fluorescence behavior and singlet oxygen generating abilities of aluminum phthalocyanine in the presence of anisotropic gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Mthethwa, Thandekile; Nyokong, Tebello, E-mail: t.nyokong@ru.ac.za

    2015-01-15

    Gold nanoparticles (spheres, rods and bipyramids) were synthesized. The nanocrystals were characterized by UV–visible spectrometry, transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The as prepared gold nanoparticles were then conjugated to a quaternized 2,(3)-tetra [2-(dimethylamino) ethanethio] substituted Al(OH) phthalocyanine (complex 1). The conjugation of phthalocyanines with gold nanoparticles resulted in a decrease in the fluorescence quantum yields and lifetimes. Conversely, an increase in the singlet oxygen quantum yields was observed for the conjugated complex 1 in the presence of AuNPs. - Highlights: • Gold nanoparticles (spheres, rods and bipyramids) were synthesized. • Gold nanoparticles were then conjugated to a quaternized ClAl phthalocyanine. • Conjugation of phthalocyanines with gold nanoparticles resulted in a decrease in the fluorescence quantum yields. • An increase in the singlet oxygen quantum yields was observed for the phthalocyanine in the presence of nanoparticles.

  9. One-Pot Synthesis of (+)-Nootkatone via Dark Singlet Oxygenation of Valencene: The Triple Role of the Amphiphilic Molybdate Catalyst

    OpenAIRE

    Bing Hong; Raphaël Lebeuf; Stéphanie Delbaere; Paul L. Alsters; Véronique Nardello-Rataj

    2016-01-01

    Efficient one-pot catalytic synthesis of (+)-nootkatone was performed from (+)-valencene using only hydrogen peroxide and amphiphilic molybdate ions. The process required no solvent and proceeded in three cascade reactions: (i) singlet oxygenation of valencene according to the ene reaction; (ii) Schenck rearrangement of one hydroperoxide into the secondary β-hydroperoxide; and (iii) dehydration of the hydroperoxide into the desired (+)-nootkatone. The solvent effect on the hydroperoxide rearr...

  10. Efficient and selective singlet oxygen sensitized NIR luminescence of a neodymium(III) complex and its application in biological imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lo, Wai-Sum [Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region (Hong Kong); Li, Hongguang [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region (Hong Kong); Law, Ga-Lai, E-mail: ga-lai.law@polyu.edu.hk [Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region (Hong Kong); Wong, Wing-Tak, E-mail: bcwtwong@polyu.edu.hk [Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region (Hong Kong); Wong, Ka-Leung, E-mail: klwong@hkbu.edu.hk [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region (Hong Kong)

    2016-01-15

    A responsive neodymium NIR emission ({sup 4}F{sub 3/2}→{sup 4}I{sub 11/2,} {sub 9/2}) was recorded upon binding with singlet oxygen (K{sub B}=1.79×10{sup 6} M{sup −1}) via the anthracene moiety. The motif ytterbium analog served as a negative control with no significant NIR enhancement/quenching with the addition of the same amount of singlet oxygen. Our complex was also found to react with {sup 1}O{sub 2} generated by a known photosensitizer TMPyP inside HeLa cells without inducing cell death and display no significant cytotoxicity. - Highlights: • A turn-on NIR-emissive {sup 1}O{sub 2} probe has been synthesized for potential biological applications. • It has a binding constant of 1.9×10{sup 6} M{sup −1} and the emission intensity has a 5-fold increase upon binding. • The probe was also found to quench singlet oxygen in vitro generated by known photosensitizer TMPyP.

  11. Oxidative damage of U937 human leukemic cells caused by hydroxyl radical results in singlet oxygen formation.

    Directory of Open Access Journals (Sweden)

    Marek Rác

    Full Text Available The exposure of human cells to oxidative stress leads to the oxidation of biomolecules such as lipids, proteins and nuclei acids. In this study, the oxidation of lipids, proteins and DNA was studied after the addition of hydrogen peroxide and Fenton reagent to cell suspension containing human leukemic monocyte lymphoma cell line U937. EPR spin-trapping data showed that the addition of hydrogen peroxide to the cell suspension formed hydroxyl radical via Fenton reaction mediated by endogenous metals. The malondialdehyde HPLC analysis showed no lipid peroxidation after the addition of hydrogen peroxide, whereas the Fenton reagent caused significant lipid peroxidation. The formation of protein carbonyls monitored by dot blot immunoassay and the DNA fragmentation measured by comet assay occurred after the addition of both hydrogen peroxide and Fenton reagent. Oxidative damage of biomolecules leads to the formation of singlet oxygen as conformed by EPR spin-trapping spectroscopy and the green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. It is proposed here that singlet oxygen is formed by the decomposition of high-energy intermediates such as dioxetane or tetroxide formed by oxidative damage of biomolecules.

  12. Correlation of in vivo tumor response and singlet oxygen luminescence detection in mTHPC-mediated photodynamic therapy

    Directory of Open Access Journals (Sweden)

    Brian C. Wilson

    2015-01-01

    Full Text Available Excited-state singlet oxygen (1O2, generated during photodynamic therapy (PDT, is believed to be the primary cytotoxic agent with a number of clinically approved photosensitizers. Its relative concentration in cells or tissues can be measured directly through its near-infrared (NIR luminescence emission, which has correlated well with in vitro cell and in vivo normal skin treatment responses. Here, its correlation with the response of tumor tissue in vivo is examined, using the photosensitizer meso-tetrahydroxyphenylchlorin (mTHPC in an animal model comprising luciferase- and green fluorescent protein (GFP-transduced gliosarcoma grown in a dorsal window chamber. The change in the bioluminescence signal, imaged pretreatment and at 2, 5 and 9 d post treatment, was used as a quantitative measure of the tumor response, which was classified in individual tumors as "non", "moderate" and "strong" in order to reduce the variance in the data. Plotting the bioluminescence-based response vs the 1O2 counts demonstrated clear correlation, indicating that 1O2 luminescence provides a valid dosimetric technique for PDT in tumor tissue.

  13. Experimental and theoretical studies of nuclear generation of ozone and its photolysis into singlet delta oxygen

    International Nuclear Information System (INIS)

    Elsayed-Ali, H.E.

    1985-01-01

    The radiation chemistry of oxygen discharges is better-studied system. The discharges were made by irradiation with high energy helium and lithium ions created by a neutron-induced reaction in boron (10). A detailed numerical model and a simplified analytical model of oxygen radiolysis have been developed to interpret the data. A summary of the data on the ozone yield from irradiation of He-O2, Ne-O2 and Ar-O2 is presented. Dose rates are also indicated. The present work appears to be the first to measure the steady state ozone concentration in noble gas-oxygen discharges and the effect of SF6 on this steady state concentration. 106 refs

  14. On the factors influencing the performance of solar reactors for water disinfection with photosensitized singlet oxygen.

    Science.gov (United States)

    Manjón, Francisco; Villén, Laura; García-Fresnadillo, David; Orellana, Guillermo

    2008-01-01

    Two solar reactors based on compound parabolic collectors (CPCs) were optimized for water disinfection by photosensitized singlet oxygen (1O2) production in the heterogeneous phase. Sensitizing materials containing Ru(II) complexes immobilized on porous silicone were produced, photochemically characterized, and successfully tested for the inactivation of up to 10(4) CFU mL(-1) of waterborne Escherichia coli (gram-negative) or Enterococcus faecalis (gram-positive) bacteria. The main factors determining the performance of the solar reactors are the type of photosensitizing material, the sensitizer loading, the CPC collector geometry (fin- vs coaxial-type), the fluid rheology, and the balance between concurrent photothermal--photolytic and 1O2 effects on the microorganisms' inactivation. In this way, at the 40 degrees N latitude of Spain, water can be disinfected on a sunny day (0.6-0.8 MJ m(-2) L(-1) accumulated solar radiation dose in the 360-700 nm range, typically 5-6 h of sunlight) with a fin-type reactor containing 0.6 m2 of photosensitizing material saturated with tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) (ca. 2.0 g m(-2)). The optimum rheological conditions require laminar-to-transitional water flow in both prototypes. The fin-type system showed better inactivation efficiency than the coaxial reactor due to a more important photolytic contribution. The durability of the sensitizing materials was tested and the operational lifetime of the photocatalyst is at least three months without any reduction in the bacteria inactivation efficiency. Solar water disinfection with 1O2-generating films is demonstrated to be an effective technique for use in isolated regions of developing countries with high yearly average sunshine.

  15. Oxygen concentration inside a functioning photosynthetic cell.

    Science.gov (United States)

    Kihara, Shigeharu; Hartzler, Daniel A; Savikhin, Sergei

    2014-05-06

    The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic photosynthetic bacteria in solitary form could have evolved ∼2.8 billion years ago without special mechanisms to protect them against reactive oxygen species. These mechanisms instead could have been developed during the following ∼500 million years while the oxygen level in the Earth's atmosphere was slowly rising. Excess oxygen concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 μM, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated oxygenic photosynthetic cells are not subjected to excessively high oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess concentration within colonies that are ∼40 μm or larger in diameter can be comparable to the oxygen concentration in air-saturated water, suggesting that species forming colonies require protection against reactive oxygen species even in the absence of oxygen in the surrounding atmosphere. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  16. A mechanistic study on the phototoxicity of atorvastatin: singlet oxygen generation by a phenanthrene-like photoproduct.

    Science.gov (United States)

    Montanaro, Sara; Lhiaubet-Vallet, Virginie; Iesce, MariaRosaria Iesce; Previtera, Lucio; Miranda, Miguel Angel

    2009-01-01

    Atorvastatin calcium (ATV) is one of the most frequently prescribed drugs worldwide. Among the adverse effects observed for this lipid-lowering agent, clinical cases of cutaneous adverse reactions have been reported and associated with photosensitivity disorders. Previous work dealing with ATV photochemistry has shown that exposure to natural sunlight in aqueous solution leads to photoproducts resulting from oxidation of the pyrrole ring and from cyclization to a phenanthrene derivative. Laser flash photolysis of ATV, at both 266 and 308 nm, led to a transient spectrum with two maxima at lambda= 360 and lambda= 580 nm (tau= 41 micro), which was assigned to the primary intermediate of the stilbene-like photocyclization. On the basis of the absence of a triplet-triplet absorption, the role of the parent drug as singlet oxygen photosensitizer can be discarded. By contrast, a stable phenanthrene-like photoproduct would be a good candidate to play this role. Laser flash photolysis of this compound showed a triplet-triplet transient absorption at lambdamax = 460 nm with a lifetime of 26 micro, which was efficiently quenched by oxygen (kq = 3 (+/-0.2) x 10(9) M(-1) s(-1)). Its potential to photosensitize formation of singlet oxygen was confirmed by spin trapping experiments, through conversion of TEMP to the stable free radical TEMPO. The photoreactivity of the phenanthrene-like photoproduct was investigated using Trp as a marker. The disappearance of the amino acid fluorescence (lambdamax = 340 nm) after increasing irradiation times at 355 nm was taken as a measurement of photodynamic oxidation. To confirm the involvement of a type II mechanism, the same experiment was also performed in D2O; this resulted in a significant enhancement of the reaction rate. On the basis of the obtained photophysical and photochemical results, the phototoxicity of atorvastatin can be attributed to singlet oxygen formation with the phenanthrene-like photoproduct as a photosensitizer.

  17. Study of the metastable singlet of molecular nitrogen and of oxygen atoms in discharges and post-discharges

    International Nuclear Information System (INIS)

    Magne, Lionel

    1991-01-01

    Whereas discharges in nitrogen, in oxygen and in their mixtures are used in many different industrial processes (surface treatment, nitridation, oxidation, and so on), in order to get a better knowledge on nitrogen electronic states, this research thesis reports the study of the metastable singlet state of molecular nitrogen, and of oxygen atoms in their fundamental state. The molecular metastable has been observed by far-UV optical emission spectroscopy, in the positive column of a continuous discharge and in time post-discharge. As far as continuous discharge is concerned, the author measured the vibrational distribution of this state. A kinetic model has been developed, and calculated vibrational distributions are in good agreement with measurements. The density of oxygen atoms in fundamental state in time post-discharge has been measured by far-UV absorption optical spectroscopy. The probability of atom re-association of glass walls is deduced from the obtained results [fr

  18. Light-triggered liposomal cargo delivery platform incorporating photosensitizers and gold nanoparticles for enhanced singlet oxygen generation and increased cytotoxicity

    Science.gov (United States)

    Kautzka, Zofia; Clement, Sandhya; Goldys, Ewa M.; Deng, Wei

    2018-02-01

    We developed light-triggered liposomes incorporating gold nanoparticles and Rose Bengal (RB), a well-known photosensitizer used for photodynamic therapy. Singlet oxygen generated by these liposomes with 532 nm light illumination was characterized by adjusting the molar ratio of lipids and gold nanoparticles while keeping the amount of RB constant. Gold nanoparticles were found to enhance the singlet oxygen generation rate, with a maximum enhancement factor of 1.75 obtained for the molar ratio of HSPC: PE-NH2: gold of 57:5:17 compared with liposomes loaded with RB alone. The experimental results could be explained by the local electric field enhancement caused by gold nanoparticles. We further assessed cellular cytotoxicity of these liposomes by encapsulating an antitumor drug, doxorubicin (Dox); such Dox loaded liposomes were applied to human colorectal cancer cells, HCT116, and exposed to light. Gold-loaded liposomes containing RB and Dox where Dox release was triggered by light were found to exhibit higher cytotoxicity, compared to the liposomes loaded with RB and Dox alone. Our results indicate that gold-loaded liposomes incorporating photosensitizers may have improved therapeutic efficacy in photodynamic therapy and chemotherapy.

  19. Photogeneration of singlet oxygen by the phenothiazine derivatives covalently bound to the surface-modified glassy carbon

    Energy Technology Data Exchange (ETDEWEB)

    Blacha-Grzechnik, Agata, E-mail: agata.blacha@polsl.pl [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Piwowar, Katarzyna; Krukiewicz, Katarzyna [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Koscielniak, Piotr; Szuber, Jacek [Institute of Electronics, Silesian University of Technology, Akademicka 16, 44-100 Gliwice (Poland); Zak, Jerzy K. [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland)

    2016-05-15

    Highlights: • The selected group of four NH{sub 2}-derivatives of phenothiazine was grafted to Glassy Carbon (GC) surface. • The grafted phenothiazines are able to generate {sup 1}O{sub 2} when activated by the radiation. • Such modified solid surfaces may find their application in the wastewater treatment. - Abstract: The selected group of four amine-derivatives of phenothiazine was covalently grafted to the glassy carbon surface in the four-step procedure consisting of the electrochemical reduction of the diazonium salt followed by the electrochemical and chemical post-modification steps. The proposed strategy involves the bonding of linker molecule to which the photosensitizer is attached. The synthesized organic layers were characterized by means of cyclic voltammetry, XPS and Raman Spectroscopy. It was shown that the phenothiazines immobilized via proposed strategy retain their photochemical properties and are able to generate {sup 1}O{sub 2} when activated by the laser radiation. The effectiveness of in situ singlet oxygen generation by those new solid photoactive materials was determined by means of UVVis spectroscopy. The reported, covalently modified solid surfaces may find their application as the singlet oxygen photogenerators in the fine chemicals’ synthesis or in the wastewater treatment.

  20. Novel approaches to singlet oxygen photosensitization in the nano- and bio-era

    OpenAIRE

    Planas Marquès, Oriol

    2017-01-01

    En aquesta tesis es detallen noves aproximacions nano- i biomoleculars amb l’objectiu de millorar la fotosensibilització i detecció d’oxigen singlet en medi biològic. En primer lloc es presenta una nova reacció fluoro- i cromogènica pel marcatge de proteïnes i nanopartícules amb derivats de porficè. Concretament, la reacció de porficens isotiocianat amb amines primàries i secundaries generen 2-aminotiazolo[4,5-c]poricè derivats amb un desplaçament concomitant en els seus espectres d’absor...

  1. Experimental and theoretical studies of nuclear generation of ozone and its photolysis into singlet delta oxygen

    International Nuclear Information System (INIS)

    Elsayed-Ali, H.E.

    1985-01-01

    A series of measurements of O 3 yield in nuclear induced O 2 and O 2 -SF 6 discharges created by bombardment with energetic particles from the 10 B(n,α) 7 Li reaction are reported. Continuous irradiation at dose ratios of 10 15 -10 17 eV.cm -3 .s -1 and pulsed irradiation (approx.10 ms FWHM) at a peak dose rate of approx.10 20 eV.cm -3 .s -1 were conducted. At the lower dose rates, SF 6 addition generally increased the ozone yield, which at the high dose rates, SF 6 addition decreased the observed ozone concentration. A numerical model was developed and applied to experimental conditions. The steady-state ozone concentration was found to be limited by the reaction O 3 - + O 3 → 2O 2 + O 2 - . A simplified analytical model of steady-state conditions was used to predict model sensitivity to various parameters. In addition to dose rate effects, pressure and temperature effect on ozone production were discussed. The present study was extended to noble gas (He, Ne, and Ar)-O 2 and noble gas - O 2 -SF 6 mixtures. Without SF 6 , steady-state ozone concentrations were found to be about an order of magnitude lower than that observed for oxygen at similar dose rates. Addition of SF 6 was found to significantly increase the steady-state ozone concentration (3-6 times) in noble gas-O 2 mixtures. The developed models were amended to study noble gas-O 2 discharges. A detailed computer model of ultraviolet irradiation of O 3 -O 2 -noble gas mixtures was presented. Dependence of O 2 (a 1 Δ/sub g/) yield on various parameters was investigated. Conditions needed to create O 2 (a 1 Δ/sub g/) concentrations sufficient for pumping an atomic iodine laser were identified. The model was tested by applying it to date on quantum yield of ozone decomposition for various mixtures and by observation of the absolute O 2 (a 1 Δ/sub g/) concentration generated under various conditions

  2. One-Pot Synthesis of (+-Nootkatone via Dark Singlet Oxygenation of Valencene: The Triple Role of the Amphiphilic Molybdate Catalyst

    Directory of Open Access Journals (Sweden)

    Bing Hong

    2016-11-01

    Full Text Available Efficient one-pot catalytic synthesis of (+-nootkatone was performed from (+-valencene using only hydrogen peroxide and amphiphilic molybdate ions. The process required no solvent and proceeded in three cascade reactions: (i singlet oxygenation of valencene according to the ene reaction; (ii Schenck rearrangement of one hydroperoxide into the secondary β-hydroperoxide; and (iii dehydration of the hydroperoxide into the desired (+-nootkatone. The solvent effect on the hydroperoxide rearrangement is herein discussed. The amphiphilic dimethyldioctyl ammonium molybdate, which is also a balanced surfactant, played a triple role in this process, as molybdate ions catalyzed at both Step 1 and Step 3 and it allowed the rapid formation of a three-phase microemulsion system that highly facilitates product recovery. Preparative synthesis of the high added value (+-nootkatone was thus performed at room temperature with an isolated yield of 46.5%. This is also the first example of a conversion of allylic hydroperoxides into ketones catalyzed by molybdate ions.

  3. Eclipta yellow vein virus enhances chlorophyll destruction, singlet oxygen production and alters endogenous redox status in Andrographis paniculata.

    Science.gov (United States)

    Khan, Asifa; Luqman, Suaib; Masood, Nusrat; Singh, Dhananjay Kumar; Saeed, Sana Tabanda; Samad, Abdul

    2016-07-01

    The infection of Eclipta yellow vein virus [EcYVV-IN, Accession No. KC476655], recently reported for the first time, on Andrographis paniculata was studied for redox-mediated alteration mechanism in infected plants. A. paniculata, an important medicinal plant, is used in traditional Indian, Chinese and modern system of medicine. Andrographolide, one of the foremost components of this plant, is known for its varied pharmacological properties. Our investigation provides insight into the effect of virus-induced changes in the singlet oxygen quenching due to the alteration in pigment content (chlorophyll and carotenoids) as well as activation of plant secondary metabolism along with defense activation leading to changes in enzymatic and non-enzymatic redox status. Due to infection, a reduction in carotenoid content was observed which leads to reduced quenching of singlet oxygen. An increased level of enzymatic (SOD and APX) and non-enzymatic antioxidant (DPPH, FRAP, RP, NO, TAC and TP) activities were also observed in virus-infected plants with a positive correlation (>0.9). However, CAT activity was diminished which could be either due to its proteolytic degradation or inactivation by superoxide anions (O(2-.)), NO or peroxynitrite radicals. A significant (p < 0.05) increase in total phenolic content was observed in the infected plants while no considerable difference was seen in the total flavonoid content. Our results highlighted the alteration in redox status caused by virus-induced biotic stress on the plants and could be useful for understanding the after effects of viral infection This study could also be helpful in developing biomimetic methods for improving the production of secondary metabolites of pharmaceutical importance. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  4. Kinetic and mechanisms of methanimine reactions with singlet and triplet molecular oxygen: Substituent and catalyst effects

    Science.gov (United States)

    Asgharzadeh, Somaie; Vahedpour, Morteza

    2018-06-01

    Methanimine reaction with O2 on singlet and triplet potential energy surfaces are investigated using B3PW91, M06-2X, MP2 and CCSD(T) methods. Thermodynamic and kinetic parameters are calculated at M06-2X method. The most favorable channel involves H-abstraction of CH2NH+O2 to the formation of HCN + H2O2 products via low level energy barrier. The catalytic effect of water molecule on HCN + H2O2 products pathway are investigated. Result shows that contribution of water molecule using complex formation with methanimine can decreases barrier energy of transition state and the reaction rate increases. Also, substituent effect of fluorine atom as deactivating group are investigated on the main reaction pathway.

  5. Investigation of the singlet delta oxygen and ozone yields from the pulsed radiolysis of oxygen and oxygen-noble gas mixtures

    International Nuclear Information System (INIS)

    Zediker, M.S.

    1984-01-01

    The experiments discussed herein were performed with a flowing gas apparatus coupled to the University of Illinois TRIGA reactor. The detectors (lambda = 1.27 μ 634 nm) were calibrated with a novel NO 2 titration scheme and the absorbed dose was estimated from the ozone concentrations measured in pure oxygen. The results of these experiments revealed an O 2 (a 1 Δ) production efficiency of 0.14% for direct nuclear pumping in an argon-oxygen mixture. Extensive modeling of the oxygen and argon-oxygen mixtures were benchmarked against these and other experiments. However, good agreement over a broad absorbed dose range was only possible if the O 4 + + O 4 - neutralization reaction was assumed to be nondissociative. In a second set of experiments with a nuclear sustained electrical discharge (low E/N), the O 2 (a 1 Δ) production efficiency was approx.0.40% for the electrical power densities examined. In addition, the O 2 (a 1 Δ) was observed to scale with the square root of the electrical power deposition but was independent of the oxygen concentration. A simple analytic model was developed which explains this behavior as a characteristic of an externally sustained discharge involving an electron attaching gas such as oxygen. The results of these experiments and the modeling of the chemical kinetics are discussed with an emphasis on optimizing the O 2 (a 1 Δ) and O 3 yields

  6. Two-Photon Irradiation of an Intracellular Singlet Oxygen Photosensitizer: Achieving Localized Sub-Cellular Excitation in Spatially-Resolved Experiments

    DEFF Research Database (Denmark)

    Pedersen, Brian Wett; Breitenbach, Thomas; Redmond, Robert W.

    2010-01-01

    The response of a given cell to spatially-resolved sub-cellular irradiation of a singlet oxygen photosensitizer (protoporphyrin IX, PpIX) using a focused laser was assessed. In these experiments, incident light was scattered over a volume greater than that defi ned by the dimensions of the laser...

  7. Preliminary study on singlet oxygen production using CeF.sub.3./sub.:Tb.sup.3+./sup.@SiO.sub.2./sub.-PpIX

    Czech Academy of Sciences Publication Activity Database

    Popovich, K.; Procházková, L.; Pelikánová, I.T.; Vlk, M.; Palkovský, M.; Jarý, Vítězslav; Nikl, Martin; Múčka, V.; Mihóková, Eva; Čuba, V.

    2016-01-01

    Roč. 90, Jul (2016), s. 325-328 ISSN 1350-4487 R&D Projects: GA ČR GA13-09876S; GA ČR GA13-28721S Institutional support: RVO:68378271 Keywords : singlet oxygen * cerium fluoride * photodynamic therapy * biofunctionalization * scintillator Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.442, year: 2016

  8. Luminescence spectroscopic observation of singlet oxygen formation in extra virgin olive oil as affected by irradiation light wavelengths, 1,4-diazabicyclo[2.2.2]octane, irradiation time, and oxygen bubbling.

    Science.gov (United States)

    Jung, Mun Y; Choi, Dong S; Park, Ki H; Lee, Bosoon; Min, David B

    2011-01-01

    A spectrofluorometer equipped with a highly sensitive near-IR InGaAs detector was used for the direct visualization of singlet oxygen emission at 1268 nm in olive oil during light irradiation with various different wavelengths. The virgin olive oil in methylene chloride (20% w/v, oxygen saturated) was irradiated at the 301, 417, 454, 483, and 668 nm, then the emission at 1268 nm, singlet oxygen dimole decaying was observed. The result showed the highest production of (1)O(2) with light irradiation at 417 nm, and followed by at 668 nm in virgin olive oil, indicating that pheophytin a and chlorophyll a were the most responsible components for the production of singlet oxygen. The UV light irradiations at the wavelength of 200, 250, and 300 nm did not induce any detectable luminescence emission at 1268 nm, but 350 nm produced weak emission at 1269 nm. The quantity of (1)O(2) produced with excitation at 350 nm was about 1/6 of that of irradiation at 417 nm. Addition of an efficient (1)O(2) quencher, 1,4-diazabicyclo[2.2.2]octane, in virgin olive oil in methylene chloride greatly decreased the luminescence emission at 1268 nm, confirming the singlet oxygen production in olive oil. Singlet oxygen production was more efficient in oxygen-purged virgin olive oil than in oxygen non-purged olive oil. This represents first report on the direct observation of singlet oxygen formation in olive oil as well as in real-food system after visible light illumination. Practical Application: The present results show the positive evidence of the singlet oxygen involvement in rapid oxidative deterioration of virgin olive oil under visible light. This paper also shows the effects of different wavelength of light irradiation on the formation of singlet oxygen in olive oil. The present results would provide important information for the understanding of the mechanism involved in rapid oxidative quality deterioration of virgin olive oil under light illumination and for searching the

  9. Effective photo-enhancement of cellular activity of fluorophore-octaarginine antisense PNA conjugates correlates with singlet oxygen formation, endosomal escape and chromophore lipophilicity

    DEFF Research Database (Denmark)

    Yarani, Reza; Shiraishi, Takehiko; Nielsen, Peter E.

    2018-01-01

    Photochemical internalization (PCI) is a cellular drug delivery method based on the generation of light-induced reactive oxygen species (ROS) causing damage to the endosomal membrane and thereby resulting in drug release to the cytoplasm. In our study a series of antisense fluorophore octaarginin...... indicate that efficient photodynamic endosomal escape is strongly dependent on the quantum yield for photochemical singlet oxygen formation, photostability as well as the lipophilicity of the chromophore....

  10. Chemical luminescence measurement of singlet oxygen generated by photodynamic therapy in solutions in real time

    Science.gov (United States)

    Luo, Shiming; Xing, Da; Zhou, Jing; Qin, Yanfang; Chen, Qun

    2005-04-01

    Photodynamic therapy (PDT) is a cancer therapy that utilizes optical energy to activate a photosensitizer drug in a target tissue. Reactive oxygen species (ROS), such as 1O2 and superoxide, are believed to be the major cytotoxic agents involved in PDT. Although current PDT dosimetry mostly involves measurements of light and photosensitizer doses delivered to a patient, the quantification of ROS production during a treatment would be the ultimate dosimetry of PDT. Technically, it is very difficult and expensive to directly measure the fluorescence from 1O2, due to its extreme short lifetime and weak signal strength. In this paper, Photofrin(R) and 635nm laser were used to generate 1O2 and superoxide in a PDT in solution. Compound 3,7- dihydro-6-{4-[2-(N"-(5-fluoresceinyl) thioureido) ethoxy] phenyl}-2- methylimidazo{1,2-a} pyrazin-3-one sodium salt,an Cyp- ridina luciferin analog commonly referred as FCLA, was used as a chemical reporter of ROS. The 532nm chemiluminescence (CL) from the reaction of the FCLA and ROS was detected with a photon multiplier tube (PMT) system operating at single photon counting mode. With the setup, we have made detections of ROS generated by PDT in real time. By varying the amount of conventional PDT dosage (photosensitizer concentration, light irradiation fluence and its delivery rate) and the amount of FCLA, the intensity of CL and its consumption rate were investigated. The results show that the intensity and temporal profile of CL are highly related to the PDT treatment parameters. This suggests that FCLA CL may provide a highly potential alternative for ROS detection during PDT.

  11. Singlet oxygen mediated apoptosis by anthrone involving lysosomes and mitochondria at ambient UV exposure

    Energy Technology Data Exchange (ETDEWEB)

    Mujtaba, Syed Faiz [Photobiology Division, (CSIR)-Indian Institute of Toxicology Research, Post Box No. 80, M.G. Marg, Lucknow 226001, Uttar Pradesh (India); College of Pharmacy, Faculty of Pharmaceutical Sciences, Pt. B.D.S University of Health Sciences, Rohtak, Haryana (India); Dwivedi, Ashish; Yadav, Neera [Photobiology Division, (CSIR)-Indian Institute of Toxicology Research, Post Box No. 80, M.G. Marg, Lucknow 226001, Uttar Pradesh (India); Ray, R.S., E-mail: ratanray.2011@rediffmail.com [Photobiology Division, (CSIR)-Indian Institute of Toxicology Research, Post Box No. 80, M.G. Marg, Lucknow 226001, Uttar Pradesh (India); Singh, Gajendra [College of Pharmacy, Faculty of Pharmaceutical Sciences, Pt. B.D.S University of Health Sciences, Rohtak, Haryana (India)

    2013-05-15

    Highlights: ► Photomodification of anthrone at ambient environmental intensities of UV-radiation. ► Phototoxicity of anthrone through type-II photodynamic reaction by generating {sup 1}O{sub 2}. ► Role of DNA damage and lipid peroxidation in anthrone phototoxicity. ► Apototic cell death and involvement of lysosomes and mitochondria. ► Up-regulation of p21 and bax concomitantly down regulation of bcl2 genes expression. -- Abstract: Anthrone a tricyclic aromatic hydrocarbon which is toxic environmental pollutant comes in the environment through photooxidation of anthracene. We have studied the photomodification of anthrone under environmental conditions. Anthrone generates reactive oxygen species (ROS) like {sup 1}O{sub 2} through Type-II photodynamic reaction. Significant intracellular ROS generation was measured through dichlorohydrofluorescein fluorescence intensity. The generation of {sup 1}O{sub 2} was further substantiated by using specific quencher like sodium azide. UV induced photodegradation of 2-deoxyguanosine and photoperoxidation of linoleic acid accorded the involvement of {sup 1}O{sub 2} in the manifestation of anthrone phototoxicity. Phototoxicity of anthrone was done on human keratinocytes (HaCaT) through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and neutral red uptake assays. Anthrone induced cell cycle arrest (G2/M-phase) and DNA damage in a concentration dependent manner. We found apoptosis as a pattern of cell death which was confirmed through sub-G1 fraction, morphological changes, caspase-3 activation, acridine orange/ethidium bromide staining and phosphatidylserine translocation. Mitochondrial depolarization and lysosomal destabilization was parallel to apoptotic process. Our RT-PCR results strongly supports our view point of apoptotic cell death through up-regulation of pro-apoptotic genes p21 and Bax, and down regulation of anti-apoptotic gene Bcl{sub 2}. Therefore, much attention should be paid to concomitant

  12. Roles of singlet oxygen and triplet excited state of dissolved organic matter formed by different organic matters in bacteriophage MS2 inactivation

    KAUST Repository

    Rosado-Lausell, Sahid L.; Wang, Hanting; Gutié rrez, Leonardo A.; Romero-Maraccini, Ofelia C.; Niu, Xi-Zhi; Gin, Karina; Croue, Jean-Philippe; Nguyen, Thanh Ha

    2013-01-01

    Inactivation of bacteriophage MS2 by reactive oxygen species (ROS) and triplet excited state of dissolved organic matter (3DOM*) produced by irradiation of natural and synthetic sensitizers with simulated sunlight of wavelengths greater than 320nm was investigated. Natural sensitizers included purified DOM isolates obtained from wastewater and river waters, and water samples collected from Singapore River, Stamford Canal, and Marina Bay Reservoir in Singapore. Linear correlations were found between MS2 inactivation rate constants (kobs) and the photo-induced reaction rate constants of 2,4,6-trimethylphenol (TMP), a probe compound shown to react mainly with 3DOM*. Linear correlations between MS2 kobs and singlet oxygen (1O2) concentrations were also found for both purified DOM isolates and natural water samples. These correlations, along with data from quenching experiments and experiments with synthetic sensitizers, Rose Bengal (RB), 3'-methoxyacetophenone (3'-MAP), and nitrite (NO2-), suggest that 1O2, 3DOM*, and hydroxyl radicals (•OH) could inactivate bacteriophage MS2. Linear correlations between MS2 kobs and Specific Ultraviolet Absorption determined at 254nm (SUVA254) were also found for both purified DOM isolates and natural samples. These results suggest the potential use of TMP as a chemical probe and SUVA254 as an indicator for virus inactivation in natural and purified DOM water samples. © 2013 Elsevier Ltd.

  13. Roles of singlet oxygen and triplet excited state of dissolved organic matter formed by different organic matters in bacteriophage MS2 inactivation

    KAUST Repository

    Rosado-Lausell, Sahid L.

    2013-09-01

    Inactivation of bacteriophage MS2 by reactive oxygen species (ROS) and triplet excited state of dissolved organic matter (3DOM*) produced by irradiation of natural and synthetic sensitizers with simulated sunlight of wavelengths greater than 320nm was investigated. Natural sensitizers included purified DOM isolates obtained from wastewater and river waters, and water samples collected from Singapore River, Stamford Canal, and Marina Bay Reservoir in Singapore. Linear correlations were found between MS2 inactivation rate constants (kobs) and the photo-induced reaction rate constants of 2,4,6-trimethylphenol (TMP), a probe compound shown to react mainly with 3DOM*. Linear correlations between MS2 kobs and singlet oxygen (1O2) concentrations were also found for both purified DOM isolates and natural water samples. These correlations, along with data from quenching experiments and experiments with synthetic sensitizers, Rose Bengal (RB), 3\\'-methoxyacetophenone (3\\'-MAP), and nitrite (NO2-), suggest that 1O2, 3DOM*, and hydroxyl radicals (•OH) could inactivate bacteriophage MS2. Linear correlations between MS2 kobs and Specific Ultraviolet Absorption determined at 254nm (SUVA254) were also found for both purified DOM isolates and natural samples. These results suggest the potential use of TMP as a chemical probe and SUVA254 as an indicator for virus inactivation in natural and purified DOM water samples. © 2013 Elsevier Ltd.

  14. Decontamination of chemical-warfare agent simulants by polymer surfaces doped with the singlet oxygen generator zinc octaphenoxyphthalocyanine.

    Science.gov (United States)

    Gephart, Raymond T; Coneski, Peter N; Wynne, James H

    2013-10-23

    Using reactive singlet oxygen (1O2), the oxidation of chemical-warfare agent (CWA) simulants has been demonstrated. The zinc octaphenoxyphthalocyanine (ZnOPPc) complex was demonstrated to be an efficient photosensitizer for converting molecular oxygen (O2) to 1O2 using broad-spectrum light (450-800 nm) from a 250 W halogen lamp. This photosensitization produces 1O2 in solution as well as within polymer matrices. The oxidation of 1-naphthol to naphthoquinone was used to monitor the rate of 1O2 generation in the commercially available polymer film Hydrothane that incorporates ZnOPPc. Using electrospinning, nanofibers of ZnOPPc in Hydrothane and polycarbonate were formed and analyzed for their ability to oxidize demeton-S, a CWA simulant, on the surface of the polymers and were found to have similar reactivity as their corresponding films. The Hydrothane films were then used to oxidize CWA simulants malathion, 2-chloroethyl phenyl sulfide (CEPS), and 2-chloroethyl ethyl sulfide (CEES). Through this oxidation process, the CWA simulants are converted into less toxic compounds, thus decontaminating the surface using only O2 from the air and light.

  15. Antibacterial nitric oxide- and singlet oxygen-releasing polystyrene nanoparticles responsive to light and temperature triggers

    Czech Academy of Sciences Publication Activity Database

    Dolanský, Jiří; Henke, P.; Malá, Z.; Žárská, L.; Kubát, Pavel; Mosinger, Jiří

    2018-01-01

    Roč. 10, č. 5 (2018), s. 2639-2648 ISSN 2040-3364 R&D Projects: GA ČR(CZ) GA16-15020S Institutional support: RVO:61388980 ; RVO:61388955 Keywords : nanofiber materials * porphyrin photosensitizers * photophysical properties * reactive oxygen Subject RIV: CA - Inorganic Chemistry; CF - Physical ; Theoretical Chemistry (UFCH-W) OBOR OECD: Inorganic and nuclear chemistry; Physical chemistry (UFCH-W) Impact factor: 7.367, year: 2016

  16. Influence of gamma radiation and singlet oxygen on nucleic acid constituents

    International Nuclear Information System (INIS)

    Balland, Alain.

    1979-10-01

    The action of single oxygen on nucleosides proved to be extremely specific of deoxy-2' guanosine. The use of high performance liquid chromatography and spectrometric techniques (IR, mass and NMR) made it possible to isolate and characterise five main products of degradation. Ionizing radiations act mainly through radical species resulting from the radiolysis of water. The effects of the presence of DNA nucleosides in irradiated aqueous solutions of thymidine were investigated. It would appear, in these conditions, that the change in radio-sensitivity of thymidine in oxygenated solution can be explained essentially in terms of the competition of hydroxyl radicals. A study of the action of gamma rays on aqueous solutions of deoxy-2' guanilyl thymidine was carried out in the absence and presence of oxygen. The significant action of neutral radical species on the 'osidic' fragment explaining the break in the phosphodiester bond was noticed. The radio-induced modifications on the substrate were characterised indirectly by enzime hydrolysis (phosphodiesterasis). In an aerated aqueous solution, the monophosphate dinucleosides modified on the thymidine motive were identified by comparison with the substances obtained by synthesis. The characterisation of new substances and the study of synthetic ones required the use of NMR. Hence the configuration study of modified nucleosides was given much room [fr

  17. Singlet oxygen autoxidation of vegetable oils: evidences for lack of synergy between β-carotene and tocopherols.

    Science.gov (United States)

    Smyk, Bogdan

    2015-09-01

    The synergy between β-carotene and tocopherols--antioxidants protecting oils from oxidation, was analyzed in a model system. The model used stripped borage and evening primrose oils. A chlorophyll extract, β-carotene and one of the tocopherols were added together or separately to the oils. Oil oxidation was initiated by singlet oxygen that was produced by chlorophylls irradiated with the use of a xenon lamp equipped with the cut-off 600 nm filter. Experiments were carried out at two mole ratios of tocopherols to β-carotene, i.e. at 1:1 and 23:1. Analyses were performed using absorption and fluorescence spectra in the UV+Vis region. The results demonstrated an antagonistic action of the antioxidants. The protective effect of unsaturated fatty acids was significantly better in the case of β-carotene compared to the tocopherols. Furthermore, tocopherols were less effective in protecting the oils in the presence of β-carotene than without it. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Influence of pulse-height discrimination threshold for photon counting on the accuracy of singlet oxygen luminescence measurement

    International Nuclear Information System (INIS)

    Lin, Huiyun; Chen, Defu; Wang, Min; Lin, Juqiang; Li, Buhong; Xie, Shusen

    2011-01-01

    Direct measurement of near-infrared (NIR) luminescence around 1270 nm is the golden standard of singlet oxygen ( 1 O 2 ) identification. In this study, the influence of pulse-height discrimination threshold on measurement accuracy of the 1 O 2 luminescence that is generated from the photoirradiation of meso-tetra (N-methyl-4-pyridyl) morphine tetra-tosylate (TMPyP) in aqueous solution was investigated by using our custom-developed detection system. Our results indicate that the discrimination threshold has a significant influence on the absolute 1 O 2 luminescence counts, and the optimal threshold for our detection system is found to be about − 41.2 mV for signal discrimination. After optimization, the derived triplet-state and 1 O 2 lifetimes of TMPyP in aqueous solution are found to be 1.73 ± 0.03 and 3.70 ± 0.04 µs, respectively, and the accuracy of measurement was further independently demonstrated using the laser flash photolysis technique

  19. Interaction of singlet oxygen with bovine serum albumin and the role of the protein nano-compartmentalization.

    Science.gov (United States)

    Giménez, Rodrigo E; Vargová, Veronika; Rey, Valentina; Turbay, M Beatriz Espeche; Abatedaga, Inés; Morán Vieyra, Faustino E; Paz Zanini, Verónica I; Mecchia Ortiz, Juan H; Katz, Néstor E; Ostatná, Veronika; Borsarelli, Claudio D

    2016-05-01

    Singlet molecular oxygen ((1)O2) contributes to protein damage triggering biophysical and biochemical changes that can be related with aging and oxidative stress. Serum albumins, such as bovine serum albumin (BSA), are abundant proteins in blood plasma with different biological functions. This paper presents a kinetic and spectroscopic study of the (1)O2-mediated oxidation of BSA using the tris(2,2'-bipyridine)ruthenium(II) cation [Ru(bpy)3](2+) as sensitizer. BSA quenches efficiently (1)O2 with a total (chemical+physical interaction) rate constant kt(BSA)=7.3(±0.4)×10(8)M(-1)s(-1), where the chemical pathway represented 37% of the interaction. This efficient quenching by BSA indicates the participation of several reactive residues. MALDI-TOF MS analysis of intact BSA confirmed that after oxidation by (1)O2, the mass protein increased the equivalent of 13 oxygen atoms. Time-resolved emission spectra analysis of BSA established that Trp residues were oxidized to N'-formylkynurenine, being the solvent-accessible W134 preferentially oxidized by (1)O2 as compared with the buried W213. MS confirmed oxidation of at least two Tyr residues to form dihydroxyphenylalanine, with a global reactivity towards (1)O2 six-times lower than for Trp residues. Despite the lack of MS evidences, kinetic and chemical analysis also suggested that residues other than Trp and Tyr, e.g. Met, must react with (1)O2. Modeling of the 3D-structure of BSA indicated that the oxidation pattern involves a random distribution of (1)O2 into BSA; allowing also the interaction of (1)O2 with buried residues by its diffusion from the bulk solvent through interconnected internal hydrophilic and hydrophobic grooves. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Preliminary study on singlet oxygen production using CeF.sub.3./sub.:Tb.sup.3+./sup.@SiO.sub.2./sub.-PpIX.

    Czech Academy of Sciences Publication Activity Database

    Popovich, K.; Procházková, L.; Pelikánová, I.T.; Vlk, M.; Palkovský, M.; Jarý, Vítězslav; Nikl, Martin; Múčka, V.; Mihóková, Eva; Čuba, V.

    2016-01-01

    Roč. 90, Jul (2016), s. 325-328 ISSN 1350-4487. [International Conference on Luminescent Detectors and Transformers of Ionizing Radiation (LUMDETR). Tartu (Estonsko), 20.09.2015-25.09.2015] R&D Projects: GA ČR GA13-09876S; GA ČR GA13-28721S Institutional support: RVO:68378271 Keywords : singlet oxygen * cerium fluoride * photodynamic therapy * biofunctionalization * scintillator Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.442, year: 2016

  1. Mitochondria Targetable Time-Gated Luminescence Probe for Singlet Oxygen Based on a β-Diketonate-Europium Complex.

    Science.gov (United States)

    Sun, Jingyan; Song, Bo; Ye, Zhiqiang; Yuan, Jingli

    2015-12-21

    Singlet oxygen ((1)O2) plays a key role in the photodynamic therapy (PDT) technique of neoplastic diseases. In this work, by using a 9,10-dimethyl-2-anthryl-containing β-diketone, 1,1,1,2,2-pentafluoro-5-(9',10'-dimethyl-2'-anthryl)-3,5-pentanedione (Hpfdap), as a (1)O2-recognition ligand, a novel β-diketonate-europium(III) complex that can act as a luminescence probe for (1)O2, [Eu(pfdap)3(tpy)] (tpy = 2,2',2″-terpyridine), has been designed and synthesized for the time-gated luminescence detection of (1)O2 in living cells. The complex is weakly luminescent due to the quenching effect of 9,10-dimethyl-2-anthryl groups. After reaction with (1)O2, accompanied by the formation of endoperoxides of 9,10-dimethyl-2-anthryl groups, the luminescence quenching disappears, so that the long-lived luminescence of the europium(III) complex is switched on. The complex showed highly selective luminescence response to (1)O2 with a remarkable luminescence enhancement. Combined with the time-gated luminescence imaging technique, the complex was successfully used as a luminescent probe for the monitoring of the time-dependent generation of (1)O2 in 5-aminolevulinic acid (a PDT drug) loaded HepG2 cells during the photodynamic process. In addition, by coloading the complex and a mitochondrial indicator, Mito-Tracker Green, into HepG2 cells, the specific localization of [Eu(pfdap)3(tpy)] molecules in mitochondria of HepG2 cells was demonstrated by confocal fluorescence imaging measurements.

  2. Singlet oxygen generation in O2 flow excited by RF discharge: I. Homogeneous discharge mode: α-mode

    International Nuclear Information System (INIS)

    Braginskiy, O V; Vasilieva, A N; Klopovskiy, K S; Kovalev, A S; Lopaev, D V; Proshina, O V; Rakhimova, T V; Rakhimov, A T

    2005-01-01

    The production and transport dynamics of O 2 (a 1 Δ g ) and O 2 (b 1 Σ g + ) molecules as well as O( 3 P) atoms has been studied in an O 2 flow excited by a 13.56 MHz RF discharge in a quartz tube at pressures of 1-20 Torr. It has been shown that the densities of O 2 (a 1 Δ g ) and O( 3 P) are saturated with increasing energy input into the discharge. The maximum yield of singlet oxygen (SO) and the O 2 dissociation degree drops with pressure. It is demonstrated that depending on the energy input the RF discharge can exist in three modes: I-in the spatially homogeneous mode or α-mode; III-in the substantially inhomogeneous mode, when plasma jets are present outside the discharge; and II-in the transient mode between modes I and III. In this paper only the homogeneous mode of RF discharge in the O 2 flow is considered in detail. A self-consistent model of the α-mode is developed, that allows us to analyse elementary processes responsible for the production and loss of O 2 (a 1 Δ g ) and O 2 (b 1 Σ g + ) molecules as well as O( 3 P) atoms in detail. To verify both the kinetic scheme of the model and the conclusions, some experiments have been carried out at lower flow velocities and higher pressures (≥10 Torr), when the stationary densities of O 2 (a 1 Δ g ), O 2 (b 1 Σ g + ) and O( 3 P) in the discharge area were established not by the escape of particles but by the losses due to the volumetric and surface reactions. The O 2 (b 1 Σ g + ) density under these conditions is determined by the balance of O 2 (b 1 Σ g + ) production by both direct electron impact and electronic excitation transfer from metastable O( 1 D) atoms and deactivation by oxygen atoms and tube walls, including quenching by ozone in the afterglow. The O( 3 P) density is determined by the balance between the production through O 2 dissociation by electron impact and heterogeneous loss at the wall recombination. The stationary density of O 2 (a 1 Δ g ) is provided by the processes of O

  3. Medical Oxygen Concentrator for Microgravity Operation, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We have all seen people carrying portable oxygen tanks or concentrators to provide critical life support respiratory oxygen. Heavy, bulky, and for O2 concentrators,...

  4. Effects of light irradiation upon photodynamic therapy based on 5-aminolevulinic acid–gold nanoparticle conjugates in K562 cells via singlet oxygen generation

    Directory of Open Access Journals (Sweden)

    Xu H

    2012-09-01

    Full Text Available Hao Xu, Chen Liu, Jiansheng Mei, Cuiping Yao, Sijia Wang, Jing Wang, Zheng Li, Zhenxi ZhangKey Laboratory of Biomedical Information Engineering of Education Ministry, Institute of Biomedical Analytical Technology and Instrumentation, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an, Shannxi, People’s Republic of ChinaPurpose: As a precursor of the potent photosensitizer protoporphyrin IX (PpIX, 5-aminolevulinic acid (5-ALA, was conjugated onto cationic gold nanoparticles (GNPs to improve the efficacy of photodynamic therapy (PDT.Methods: Cationic GNPs reduced by branched polyethyleneimine and 5-ALA were conjugated onto the cationic GNPs by creating an electrostatic interaction at physiological pH. The efficacy of ALA-GNP conjugates in PDT was investigated under irradiation with a mercury lamp (central wavelength of 395 nm and three types of light-emitting diode arrays (central wavelengths of 399, 502, and 621 nm, respectively. The impacts of GNPs on PDT were then analyzed by measuring the intracellular PpIX levels in K562 cells and the singlet oxygen yield of PpIX under irradiation.Results: The 2 mM ALA-GNP conjugates showed greater cytotoxicity against K562 cells than ALA alone. Light-emitting diode (505 nm irradiation of the conjugates caused a level of K562 cell destruction similar to that with irradiation by a mercury lamp, although it had no adverse effects on drug-free control cells. These results may be attributed to the singlet oxygen yield of PpIX, which can be enhanced by GNPs.Conclusion: Under irradiation with a suitable light source, ALA-GNP conjugates can effectively destroy K562 cells. The technique offers a new strategy of PDT.Keywords: nonradiative energy transfer, photodamage, protoporphyrin IX, selective destruction, singlet oxygen sensor green reagent, surface plasmon resonance

  5. Protection by DABCO against inactivation of transforming DNA by near-ultraviolet light: action spectra and implications for involvement of singlet oxygen

    International Nuclear Information System (INIS)

    Peak, J.G.; Peak, M.J.; Foote, C.S.

    1981-01-01

    Diazobicyclo (2.2.2) octane (DABCO) protects the genetic activity of purified transforming Bacillus subtilis DNA against inactivation by near-, but not far-, UV light. The maximum dose-modifying factor is 0.4, at 0.1 M DABCO. Maximal protection is at about 350 nm and no protection occurs below 313 nm. The spectrum for protection is similar to that described for 2-aminoethylisothiouronium bromide hydrobromide. The relevance of these observations with regard to the role of singlet oxygen in near-UV effects is discussed. (author)

  6. Influence of singlet oxygen (1O2) generated by a lipophilic photosensitizer (Pyropheophorbide-a, PPa) on membrane and firing properties of cultured hippocampus neurons

    DEFF Research Database (Denmark)

    Breitenbach, Thomas; Ogilby, Peter Remsen; Lambert, John D. C.

    2008-01-01

    . The spiking pattern was altered significantly, reflected by changes in spike threshold, frequency and tendency for fast APs to be followed by a plateau phase. These effects were correlated with the intensity and/or duration of illumination. Since we have previously documented that the lifetime and diffusion...... range of singlet oxygen are very small, its effects will be restricted. The intra-membrane generated 1O2 alters the composition of the lipid and also proteins or channels. This is reflected both in the immediate response to low irradiation-dose and in formation of long plateaus, which could be caused...

  7. Relationship between symmetry of porphyrinic pi-conjugated systems and singlet oxygen (1Delta g) yields: low-symmetry tetraazaporphyrin derivatives.

    Science.gov (United States)

    Ishii, Kazuyuki; Itoya, Hatsumi; Miwa, Hideya; Fujitsuka, Mamoru; Ito, Osamu; Kobayashi, Nagao

    2005-07-07

    We have investigated the excited-state properties and singlet oxygen ((1)Delta(g)) generation mechanism in phthalocyanines (4M; M = H(2), Mg, or Zn) and in low-symmetry metal-free, magnesium, and zinc tetraazaporphyrins (TAPs), that is, monobenzo-substituted (1M), adjacently dibenzo-substituted (2AdM), oppositely dibenzo-substituted (2OpM), and tribenzo-substituted (3M) TAP derivatives, whose pi conjugated systems were altered by fusing benzo rings. The S(1)(x) and S(1)(y) states (these lowest excited singlet states are degenerate in D(4)(h) symmetry) split in the low-symmetry TAP derivatives. The excited-state energies were quantitatively determined from the electronic absorption spectra. The lowest excited triplet (T(1)(x)) energies were also determined from phosphorescence spectra, while the second lowest excited triplet (T(1)(y)) states were evaluated by using the energy splitting between the T(1)(x) and T(1)(y) states previously reported (Miwa, H.; Ishii, K.; Kobayashi, N. Chem. Eur. J. 2004, 10, 4422-4435). The singlet oxygen quantum yields (Phi(Delta)) are strongly dependent on the pi conjugated system. In particular, while the Phi(Delta) value of 2AdH(2) is smallest in our system, that of 2OpH(2), an isomer of 2AdH(2), is larger than that of 4Zn, in contrast to the heavy atom effect. The relationship between the molecular structure and Phi(Delta) values can be transformed into a relationship between the S(1)(x) --> T(1)(y) intersystem crossing rate constant (k(ISC)) and the energy difference between the S(1)(x) and T(1)(y) states (DeltaE(S)(x)(T)(y)). In each of the Zn, Mg, and metal-free compounds, the Phi(Delta)/tau(F) values (tau(F): fluorescence lifetime), which are related to the k(ISC) values, are proportional to exp(-DeltaE(S)(x)(T)(y)), indicating that singlet oxygen ((1)Delta(g)) is produced via the T(1)(y) state and that the S(1)(x) --> T(1)(y) ISC process follows the energy-gap law. From the viewpoint of photodynamic therapy, our methodology

  8. Generation of Triplet Excited States via Photoinduced Electron Transfer in meso-anthra-BODIPY: Fluorogenic Response toward Singlet Oxygen in Solution and in Vitro

    KAUST Repository

    Filatov, Mikhail A.; Karuthedath, Safakath; Polestshuk, Pavel M.; Savoie, Huguette; Flanagan, Keith J.; Sy, Cindy; Sitte, Elisabeth; Telitchko, Maxime; Laquai, Fré dé ric; Boyle, Ross W.; Senge, Mathias O.

    2017-01-01

    Heavy atom-free BODIPY-anthracene dyads (BADs) generate locally excited triplet states by way of photoinduced electron transfer (PeT), followed by recombination of the resulting charge-separated states (CSS). Subsequent quenching of the triplet states by molecular oxygen produces singlet oxygen (1O2), which reacts with the anthracene moiety yielding highly fluorescent species. The steric demand of the alkyl substituents in the BODIPY subunit defines the site of 1O2 addition. Novel bis- and tetraepoxides and bicyclic acetal products, arising from rearrangements of anthracene endoperoxides were isolated and characterized. 1O2 generation by BADs in living cells enables visualization of the dyads distribution, promising new imaging applications.

  9. Generation of Triplet Excited States via Photoinduced Electron Transfer in meso-anthra-BODIPY: Fluorogenic Response toward Singlet Oxygen in Solution and in Vitro

    KAUST Repository

    Filatov, Mikhail A.

    2017-04-14

    Heavy atom-free BODIPY-anthracene dyads (BADs) generate locally excited triplet states by way of photoinduced electron transfer (PeT), followed by recombination of the resulting charge-separated states (CSS). Subsequent quenching of the triplet states by molecular oxygen produces singlet oxygen (1O2), which reacts with the anthracene moiety yielding highly fluorescent species. The steric demand of the alkyl substituents in the BODIPY subunit defines the site of 1O2 addition. Novel bis- and tetraepoxides and bicyclic acetal products, arising from rearrangements of anthracene endoperoxides were isolated and characterized. 1O2 generation by BADs in living cells enables visualization of the dyads distribution, promising new imaging applications.

  10. Singlet oxygen and ROS in a new light: low-dose subcellular photodynamic treatment enhances proliferation at the single cell level.

    Science.gov (United States)

    Blázquez-Castro, Alfonso; Breitenbach, Thomas; Ogilby, Peter R

    2014-09-01

    Two-photon excitation of a sensitizer with a focused laser beam was used to create a spatially-localized subcellular population of reactive oxygen species, ROS, in single HeLa cells. The sensitizer used was protoporphyrin IX, PpIX, endogenously derived from 5-aminolevulinic acid delivered to the cells. Although we infer that singlet oxygen, O2(a(1)Δg), is one ROS produced upon irradiation of PpIX under these conditions, it is possible that the superoxide ion, O2(-˙), may also play a role in this system. With a "high" dose of PpIX-sensitized ROS, the expected death of the cell was observed. However, under "low dose" conditions, clear signs of cell proliferation were observed. The present results facilitate studies of ROS-mediated signalling in imaging-based single cell experiments.

  11. Aerobic growth at nanomolar oxygen concentrations

    DEFF Research Database (Denmark)

    Stolper, Daniel Aaron; Revsbech, Niels Peter; Canfield, Donald Eugene

    2010-01-01

    that Escherichia coli K-12, chosen for its well-understood biochemistry, rapid growth rate, and low-oxygen-affinity terminal oxidase, grows at oxygen levels of ≤ 3 nM, two to three orders of magnitude lower than previously observed for aerobes. Our study expands both the environmental range and temporal history...... of aerobic organisms....

  12. Aerobic growth at nanomolar oxygen concentrations

    DEFF Research Database (Denmark)

    Stolper, Daniel; Revsbech, Niels Peter; Canfield, Donald Eugene

    2010-01-01

    that Escherichia coli K-12, chosen for its well-understood biochemistry, rapid growth rate, and low-oxygen-affinity terminal oxidase, grows at oxygen levels of ≤ 3 nM, two to three orders of magnitude lower than previously observed for aerobes. Our study expands both the environmental range and temporal history...... of aerobic organisms....

  13. Aquatic respiration rate measurements at low oxygen concentrations.

    Directory of Open Access Journals (Sweden)

    Moritz Holtappels

    Full Text Available Despite its huge ecological importance, microbial oxygen respiration in pelagic waters is little studied, primarily due to methodological difficulties. Respiration measurements are challenging because of the required high resolution of oxygen concentration measurements. Recent improvements in oxygen sensing techniques bear great potential to overcome these limitations. Here we compare 3 different methods to measure oxygen consumption rates at low oxygen concentrations, utilizing amperometric Clark type sensors (STOX, optical sensors (optodes, and mass spectrometry in combination with (18-18O2 labeling. Oxygen concentrations and consumption rates agreed well between the different methods when applied in the same experimental setting. Oxygen consumption rates between 30 and 400 nmol L(-1 h(-1 were measured with high precision and relative standard errors of less than 3%. Rate detection limits in the range of 1 nmol L(-1 h(-1 were suitable for rate determinations in open ocean water and were lowest at the lowest applied O2 concentration.

  14. A Solar Powered, Ceramic Oxygen Concentrator

    Data.gov (United States)

    National Aeronautics and Space Administration — Childhood pneumonia, which is treated with oxygen therapy, is a leading cause of death in children. Many children in developing countries lack access to medical...

  15. Modulation of the Singlet Oxygen Generation from the Double Strand DNA-SYBR Green I Complex Mediated by T-Melamine-T Mismatch for Visual Detection of Melamine.

    Science.gov (United States)

    Hu, Hao; Zhang, Jinyi; Ding, Yu; Zhang, Xinfeng; Xu, Kailai; Hou, Xiandeng; Wu, Peng

    2017-05-02

    Singlet oxygen ( 1 O 2 ), generated via photosensitization, has been proved to oxidize chromogenic substrates with neither H 2 O 2 oxidation nor enzyme (horseradish peroxidase, HRP) catalysis. Of the various methods for modulation of the 1 O 2 generation, DNA-controlled photosensitization received great attention. Therefore, integration of the formation/deformation DNA structures with DNA-controlled photosensitization will be extremely appealing in visual biosensor developments. Here, the stable melamine-thymine complex was explored in combination with DNA-controlled photosensitization for visual detection of melamine. A T-rich single stand DNA was utilized as the recognition unit. Upon the formation of the T-M-T complex, double stand DNA was formed, which was ready for the binding of SYBR Green I and activated the photosensitization. Subsequent oxidation of TMB allowed visual detection of melamine in dairy products, with spike-recoveries ranging from 94% to 106%.

  16. Single photon counting fluorescence lifetime detection of pericellular oxygen concentrations.

    Science.gov (United States)

    Hosny, Neveen A; Lee, David A; Knight, Martin M

    2012-01-01

    Fluorescence lifetime imaging microscopy offers a non-invasive method for quantifying local oxygen concentrations. However, existing methods are either invasive, require custom-made systems, or show limited spatial resolution. Therefore, these methods are unsuitable for investigation of pericellular oxygen concentrations. This study describes an adaptation of commercially available equipment which has been optimized for quantitative extracellular oxygen detection with high lifetime accuracy and spatial resolution while avoiding systematic photon pile-up. The oxygen sensitive fluorescent dye, tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate [Ru(bipy)(3)](2+), was excited using a two-photon excitation laser. Lifetime was measured using a Becker & Hickl time-correlated single photon counting, which will be referred to as a TCSPC card. [Ru(bipy)(3)](2+) characterization studies quantified the influences of temperature, pH, cellular culture media and oxygen on the fluorescence lifetime measurements. This provided a precisely calibrated and accurate system for quantification of pericellular oxygen concentration based on measured lifetimes. Using this technique, quantification of oxygen concentrations around isolated viable chondrocytes, seeded in three-dimensional agarose gel, revealed a subpopulation of cells that exhibited significant spatial oxygen gradients such that oxygen concentration reduced with increasing proximity to the cell. This technique provides a powerful tool for quantifying spatial oxygen gradients within three-dimensional cellular models.

  17. C60 and Sc3N@C80(TMB-PPO derivatives as constituents of singlet oxygen generating, thiol-ene polymer nanocomposites

    Directory of Open Access Journals (Sweden)

    Ashli R. Toles

    2016-07-01

    Full Text Available Numerous functionalization methods have been employed to increase the solubility, and therefore, the processability of fullerenes in composite structures, and of these radical addition reactions continue to be an important methodology. C60 and Sc3N@C80 derivatives were prepared via radical addition of the photodecomposition products from the commercial photoinitiator TMB-PPO, yielding C60(TMB-PPO5 and Sc3N@C80(TMB-PPO3 as preferred soluble derivatives obtained in high yields. Characterization of the mixture of isomers using standard techniques suggests an overall 1PPO:6TMB ratio of addends, reflecting the increased reactivity of the carbon radical. Although, a higher percentage of PPO is observed in the Sc3N@C80(TMB-PPO3 population, perhaps due to reverse electronic requirements of the substrate. Visually dispersed thiol-ene nanocomposites with low extractables were prepared using two monomer compositions (PETMP:TTT and TMPMP:TMPDE with increasing fullerene derivative loading to probe network structure-property relationships. Thermal stability of the derivatives and the resulting networks decreased with increased functionality and at high fullerene loadings, respectively. TMPMP:TMPDE composite networks show well-dispersed derivatives via TEM imaging, and increasing Tg’s with fullerene loading, as expected for the incorporation of a more rigid network component. PETMP:TTT composites show phase separation in TEM, which is supported by the observed Tg’s. Singlet oxygen generation of the derivatives decreases with increased functionality; however, this is compensated for by the tremendous increase in solubility in organic solvents and miscibility with monomers. Most importantly, singlet oxygen generation from the composites increased with fullerene derivative loading, with good photostability of the networks.

  18. Effects of oxygen concentration on atmospheric pressure dielectric barrier discharge in Argon-Oxygen Mixture

    Science.gov (United States)

    Li, Xuechun; Li, Dian; Wang, Younian

    2016-09-01

    A dielectric barrier discharge (DBD) can generate a low-temperature plasma easily at atmospheric pressure and has been investigated for applications in trials in cancer therapy, sterilization, air pollution control, etc. It has been confirmed that reactive oxygen species (ROS) play a key role in the processes. In this work, we use a fluid model to simulate the plasma characteristics for DBD in argon-oxygen mixture. The effects of oxygen concentration on the plasma characteristics have been discussed. The evolution mechanism of ROS has been systematically analyzed. It was found that the ground state oxygen atoms and oxygen molecular ions are the dominated oxygen species under the considered oxygen concentrations. With the oxygen concentration increasing, the densities of electrons, argon atomic ions, resonance state argon atoms, metastable state argon atoms and excited state argon atoms all show a trend of decline. The oxygen molecular ions density is high and little influenced by the oxygen concentration. Ground state oxygen atoms density tends to increase before falling. The ozone density increases significantly. Increasing the oxygen concentration, the discharge mode begins to change gradually from the glow discharge mode to Townsend discharge mode. Project supported by the National Natural Science Foundation of China (Grant No. 11175034).

  19. Monitoring and measurement of oxygen concentrations in liquid sodium

    International Nuclear Information System (INIS)

    Smith, D.L.

    1976-01-01

    The measurement of oxygen concentrations in sodium at levels of interest for LMFBR applications is reviewed. Additional data are presented to support the validity of the vanadium-equilibration method as a reference for determination of oxygen concentrations in sodium at levels equal to or less than 15 ppM. Operating experience with electrochemical oxygen meters that have a thoria-yttria electrolyte and a Na--Na 2 O reference electrode is described. Meter lifetimes in excess of one year have generally been achieved for operating temperatures of 352 and 402 0 C, and fairly stable emfs have been observed for periods of several months. 7 fig, 21 references

  20. Interaction of singlet oxygen with bovine serum albumin and the role of the protein nano-compartmentalization

    Czech Academy of Sciences Publication Activity Database

    Gimenez, R.E.; Vargová, Veronika; Rey, V.; Turbay, M.B.E.; Abatedaga, I.; Vieyra, F.E.M.; Zanini, V.I.P.; Ortiz, J.H.M.; Katz, N. E.; Ostatná, Veronika; Borsarelli, C.D.

    2016-01-01

    Roč. 94, MAY2016 (2016), s. 99-109 ISSN 0891-5849 R&D Projects: GA ČR GBP206/12/G151 Institutional support: RVO:68081707 Keywords : oxidative stress * molecular-oxygen * amino - acids Subject RIV: BO - Biophysics Impact factor: 5.606, year: 2016

  1. Dislocation behavior of surface-oxygen-concentration controlled Si wafers

    International Nuclear Information System (INIS)

    Asazu, Hirotada; Takeuchi, Shotaro; Sannai, Hiroya; Sudo, Haruo; Araki, Koji; Nakamura, Yoshiaki; Izunome, Koji; Sakai, Akira

    2014-01-01

    We have investigated dislocation behavior in the surface area of surface-oxygen-concentration controlled Si wafers treated by a high temperature rapid thermal oxidation (HT-RTO). The HT-RTO process allows us to precisely control the interstitial oxygen concentration ([O i ]) in the surface area of the Si wafers. Sizes of rosette patterns, generated by nano-indentation and subsequent thermal annealing at 900 °C for 1 h, were measured for the Si wafers with various [O i ]. It was found that the rosette size decreases in proportion to the − 0.25 power of [O i ] in the surface area of the Si wafers, which were higher than [O i ] of 1 × 10 17 atoms/cm 3 . On the other hand, [O i ] of lower than 1 × 10 17 atoms/cm 3 did not affect the rosette size very much. These experimental results demonstrate the ability of the HT-RTO process to suppress the dislocation movements in the surface area of the Si wafer. - Highlights: • Surface-oxygen-concentration controlled Si wafers have been made. • The oxygen concentration was controlled by high temperature rapid thermal oxidation. • Dislocation behavior in the surface area of the Si wafers has been investigated. • Rosette size decreased with increasing of interstitial oxygen atoms. • The interstitial oxygen atoms have a pinning effect of dislocations at the surface

  2. Monte Carlo modeling of in vivo protoporphyrin IX fluorescence and singlet oxygen production during photodynamic therapy for patients presenting with superficial basal cell carcinomas

    Science.gov (United States)

    Valentine, Ronan M.; Brown, C. Tom A.; Moseley, Harry; Ibbotson, Sally; Wood, Kenny

    2011-04-01

    We present protoporphyrin IX (PpIX) fluorescence measurements acquired from patients presenting with superficial basal cell carcinoma during photodynamic therapy (PDT) treatment, facilitating in vivo photobleaching to be monitored. Monte Carlo (MC) simulations, taking into account photobleaching, are performed on a three-dimensional cube grid, which represents the treatment geometry. Consequently, it is possible to determine the spatial and temporal changes to the origin of collected fluorescence and generated singlet oxygen. From our clinical results, an in vivo photobleaching dose constant, β of 5-aminolaevulinic acid-induced PpIX fluorescence is found to be 14 +/- 1 J/cm2. Results from our MC simulations suggest that an increase from our typical administered treatment light dose of 75-150 J/cm2 could increase the effective PDT treatment initially achieved at a depth of 2.7-3.3 mm in the tumor, respectively. Moreover, this increase reduces the surface PpIX fluorescence from 0.00012 to 0.000003 of the maximum value recorded before treatment. The recommendation of administrating a larger light dose, which advocates an increase in the treatment time after surface PpIX fluorescence has diminished, remains valid for different sets of optical properties and therefore should have a beneficial outcome on the total treatment effect.

  3. Correlation among Singlet-Oxygen Quenching, Free-Radical Scavenging, and Excited-State Intramolecular-Proton-Transfer Activities in Hydroxyflavones, Anthocyanidins, and 1-Hydroxyanthraquinones.

    Science.gov (United States)

    Nagaoka, Shin-Ichi; Bandoh, Yuki; Nagashima, Umpei; Ohara, Keishi

    2017-10-26

    Singlet-oxygen ( 1 O 2 ) quenching, free-radical scavenging, and excited-state intramolecular proton-transfer (ESIPT) activities of hydroxyflavones, anthocyanidins, and 1-hydroxyanthraquinones were studied by means of laser, stopped-flow, and steady-state spectroscopies. In hydroxyflavones and anthocyanidins, the 1 O 2 quenching activity positively correlates to the free-radical scavenging activity. The reason for this correlation can be understood by considering that an early step of each reaction involves electron transfer from the unfused phenyl ring (B-ring), which is singly bonded to the bicyclic chromen or chromenylium moiety (A- and C-rings). Substitution of an electron-donating OH group at B-ring enhances the electron transfer leading to activation of the 1 O 2 quenching and free-radical scavenging. In 3-hydroxyflavones, the OH substitution at B-ring reduces the activity of ESIPT within C-ring, which can be explained in terms of the nodal-plane model. As a result, the 1 O 2 quenching and free-radical scavenging activities negatively correlate to the ESIPT activity. A catechol structure at B-ring is another factor that enhances the free-radical scavenging in hydroxyflavones. In contrast to these hydroxyflavones, 1-hydroxyanthraquinones having an electron-donating OH substituent adjacent to the O-H---O═C moiety susceptible to ESIPT do not show a simple correlation between their 1 O 2 quenching and ESIPT activities, because the OH substitution modulates these reactions.

  4. Ligand-based photooxidations of dithiomaltolato complexes of Ru(II) and Zn(II): photolytic CH activation and evidence of singlet oxygen generation and quenching.

    Science.gov (United States)

    Bruner, Britain; Walker, Malin Backlund; Ghimire, Mukunda M; Zhang, Dong; Selke, Matthias; Klausmeyer, Kevin K; Omary, Mohammad A; Farmer, Patrick J

    2014-08-14

    The complex [Ru(bpy)2(ttma)](+) (bpy = 2,2'-bipyridine; ttma = 3-hydroxy-2-methyl-thiopyran-4-thionate, 1, has previously been shown to undergo an unusual C-H activation of the dithiomaltolato ligand upon outer-sphere oxidation. The reaction generated alcohol and aldehyde products 2 and 3 from C-H oxidation of the pendant methyl group. In this report, we demonstrate that the same products are formed upon photolysis of 1 in presence of mild oxidants such as methyl viologen, [Ru(NH3)6](3+) and [Co(NH3)5Cl](2+), which do not oxidize 1 in the dark. This reactivity is engendered only upon excitation into an absorption band attributed to the ttma ligand. Analogous experiments with the homoleptic Zn(ttma)2, 4, also result in reduction of electron acceptors upon excitation of the ttma absorption band. Complexes 1 and 4 exhibit short-lived visible fluorescence and long-lived near-infrared phosphorescence bands. Singlet oxygen is both generated and quenched during aerobic excitation of 1 or 4, but is not involved in the C-H activation process.

  5. Effects of the cryptochrome CryB from Rhodobacter sphaeroides on global gene expression in the dark or blue light or in the presence of singlet oxygen.

    Directory of Open Access Journals (Sweden)

    Sebastian Frühwirth

    Full Text Available Several regulators are controlling the formation of the photosynthetic apparatus in the facultatively photosynthetic bacterium Rhodobacter sphaeroides. Among the proteins affecting photosynthesis gene expression is the blue light photoreceptor cryptochrome CryB. This study addresses the effect of CryB on global gene expression. The data reveal that CryB does not only influence photosynthesis gene expression but also genes for the non-photosynthetic energy metabolism like citric acid cycle and oxidative phosphorylation. In addition several genes involved in RNA processing and in transcriptional regulation are affected by a cryB deletion. Although CryB was shown to undergo a photocycle it does not only affect gene expression in response to blue light illumination but also in response to singlet oxygen stress conditions. While there is a large overlap in these responses, some CryB-dependent effects are specific for blue-light or photooxidative stress. In addition to protein-coding genes some genes for sRNAs show CryB-dependent expression. These findings give new insight into the function of bacterial cryptochromes and demonstrate for the first time a function in the oxidative stress response.

  6. Reinforcement corrosion in alkaline chloride media with reduced oxygen concentrations

    International Nuclear Information System (INIS)

    Andrade, C.; Fullea, J.; Toro, L.; Martinez, I.; Rebolledo, N.

    2013-01-01

    It is commonly considered that the corrosion of steel in concrete is controlled by the oxygen content of the pore solution and there are service life models that relate the corrosion rate to the amount of oxygen. It is also commonly believed that in water saturated conditions the oxygen content in the pores is negligible and that underwater there is no risk of depassivation and the corrosion rate is very low. However, the available data on corrosion rates in immersed conditions do not indicate such performance; on the contrary corrosion develops when sufficient chloride reaches the reinforcement. In the present paper, results are presented for tests performed in alkaline chloride solutions that were purged with nitrogen to reduce the oxygen content. The results indicate that at very low oxygen concentrations, corrosion may develop in the presence of chlorides. The presence or absence of corrosion is influenced by the amount of chloride, the corrosion potential and the steel surface condition. (authors)

  7. IMPACT OF OXYGEN CONCENTRATION ON ZEBRA MUSSEL MORTALITY

    Energy Technology Data Exchange (ETDEWEB)

    Daniel P. Molloy

    2003-01-27

    These tests have indicated that the bacterium Pseudomonas fluorescens strain CL0145A is effective at killing zebra mussels in environments having dissolved oxygen (DO) concentrations ranging from very low to very high. The results suggest that the highest mussel kill can be achieved in moderately to highly aerated environments, while kill may be 0-20% lower under conditions of very low oxygen. For example, under highly oxygenated conditions 97% kill was achieved while conditions having low DO produced 79% mussel kill. Service water measured in a local power plant indicated that DO concentrations were in the range of 8-9 ppm (e.g., highly aerated) within their pipes. Therefore, we will not expect to see decreases in the efficacy of CL0145A treatments due to oxygen levels within such power plant pipes.

  8. IMPACT OF OXYGEN CONCENTRATION ON ZEBRA MUSSEL MORTALITY

    International Nuclear Information System (INIS)

    Molloy, Daniel P.

    2003-01-01

    These tests have indicated that the bacterium Pseudomonas fluorescens strain CL0145A is effective at killing zebra mussels in environments having dissolved oxygen (DO) concentrations ranging from very low to very high. The results suggest that the highest mussel kill can be achieved in moderately to highly aerated environments, while kill may be 0-20% lower under conditions of very low oxygen. For example, under highly oxygenated conditions 97% kill was achieved while conditions having low DO produced 79% mussel kill. Service water measured in a local power plant indicated that DO concentrations were in the range of 8-9 ppm (e.g., highly aerated) within their pipes. Therefore, we will not expect to see decreases in the efficacy of CL0145A treatments due to oxygen levels within such power plant pipes

  9. Application of Nanosize Zeolite Molecular Sieves for Medical Oxygen Concentration

    Directory of Open Access Journals (Sweden)

    Mingfei Pan

    2017-07-01

    Full Text Available The development of a portable oxygen concentrator is of prime significance for patients with respiratory problems. This paper presents a portable concentrator prototype design using the pressure/vacuum swing adsorption (PVSA cycle with a deep evacuation step (−0.82 barg instead of desorption with purge flow to simplify the oxygen production process. The output of the oxygen concentrator is a ~90 vol % enriched oxygen stream in a continuous adsorption and desorption cycle (cycle time ~90 s. The size of the adsorption column is 3 cm in diameter and 20 cm in length. A Li+ exchanged 13X nanosize zeolite is used as the adsorbent to selectively adsorb nitrogen from air. A dynamic model of the pressure and vacuum swing adsorption units was developed to study the pressurization and depressurization process inside the microporous area of nanosized zeolites. The describing equations were solved using COMSOL Multiphysics Chemical Engineering module. The output flow rate and oxygen concentration results from the simulation model were compared with the experimental data. Velocity and concentration profiles were obtained to study the adsorption process and optimize the operational parameters.

  10. Singlet molecular oxygen generation by light-activated DHN-melanin of the fungal pathogen Mycosphaerella fijiensis in black Sigatoka disease of bananas.

    Directory of Open Access Journals (Sweden)

    Miguel J Beltrán-García

    Full Text Available In pathogenic fungi, melanin contributes to virulence, allowing tissue invasion and inactivation of the plant defence system, but has never been implicated as a factor for host cell death, or as a light-activated phytotoxin. Our research shows that melanin synthesized by the fungal banana pathogen Mycosphaerella fijiensis acts as a virulence factor through the photogeneration of singlet molecular oxygen O2 (1Δg. Using analytical tools, including elemental analysis, ultraviolet/infrared absorption spectrophometry and MALDI-TOF mass spectrometry analysis, we characterized both pigment content in mycelia and secreted to the culture media as 1,8-dihydroxynaphthalene (DHN-melanin type compound. This is sole melanin-type in M. fijiensis. Isolated melanins irradiated with a Nd:YAG laser at 532 nm produced monomol light emission at 1270 nm, confirming generation of O2 (1Δg, a highly reactive oxygen specie (ROS that causes cellular death by reacting with all cellular macromolecules. Intermediary polyketides accumulated in culture media by using tricyclazole and pyroquilon (two inhibitors of DHN-melanin synthesis were identified by ESI-HPLC-MS/MS. Additionally, irradiation at 532 nm of that mixture of compounds and whole melanized mycelium also generated O2 (1Δg. A pigmented-strain generated more O2 (1Δg than a strain with low melanin content. Banana leaves of cultivar Cavendish, naturally infected with different stages of black Sigatoka disease, were collected from field. Direct staining of the naturally infected leaf tissues showed the presence of melanin that was positively correlated to the disease stage. We also found hydrogen peroxide (H2O2 but we cannot distinguish the source. Our results suggest that O2 (1Δg photogenerated by DHN-melanin may be involved in the destructive effects of Mycosphaerella fijiensis on banana leaf tissues. Further studies are needed to fully evaluate contributions of melanin-mediated ROS to microbial pathogenesis.

  11. Singlet molecular oxygen generation by light-activated DHN-melanin of the fungal pathogen Mycosphaerella fijiensis in black Sigatoka disease of bananas.

    Science.gov (United States)

    Beltrán-García, Miguel J; Prado, Fernanda M; Oliveira, Marilene S; Ortiz-Mendoza, David; Scalfo, Alexsandra C; Pessoa, Adalberto; Medeiros, Marisa H G; White, James F; Di Mascio, Paolo

    2014-01-01

    In pathogenic fungi, melanin contributes to virulence, allowing tissue invasion and inactivation of the plant defence system, but has never been implicated as a factor for host cell death, or as a light-activated phytotoxin. Our research shows that melanin synthesized by the fungal banana pathogen Mycosphaerella fijiensis acts as a virulence factor through the photogeneration of singlet molecular oxygen O2 (1Δg). Using analytical tools, including elemental analysis, ultraviolet/infrared absorption spectrophometry and MALDI-TOF mass spectrometry analysis, we characterized both pigment content in mycelia and secreted to the culture media as 1,8-dihydroxynaphthalene (DHN)-melanin type compound. This is sole melanin-type in M. fijiensis. Isolated melanins irradiated with a Nd:YAG laser at 532 nm produced monomol light emission at 1270 nm, confirming generation of O2 (1Δg), a highly reactive oxygen specie (ROS) that causes cellular death by reacting with all cellular macromolecules. Intermediary polyketides accumulated in culture media by using tricyclazole and pyroquilon (two inhibitors of DHN-melanin synthesis) were identified by ESI-HPLC-MS/MS. Additionally, irradiation at 532 nm of that mixture of compounds and whole melanized mycelium also generated O2 (1Δg). A pigmented-strain generated more O2 (1Δg) than a strain with low melanin content. Banana leaves of cultivar Cavendish, naturally infected with different stages of black Sigatoka disease, were collected from field. Direct staining of the naturally infected leaf tissues showed the presence of melanin that was positively correlated to the disease stage. We also found hydrogen peroxide (H2O2) but we cannot distinguish the source. Our results suggest that O2 (1Δg) photogenerated by DHN-melanin may be involved in the destructive effects of Mycosphaerella fijiensis on banana leaf tissues. Further studies are needed to fully evaluate contributions of melanin-mediated ROS to microbial pathogenesis.

  12. Singlet oxygen sensitizing materials based on porous silicone: photochemical characterization, effect of dye reloading and application to water disinfection with solar reactors.

    Science.gov (United States)

    Manjón, Francisco; Santana-Magaña, Montserrat; García-Fresnadillo, David; Orellana, Guillermo

    2010-06-01

    Photogeneration of singlet molecular oxygen ((1)O(2)) is applied to organic synthesis (photooxidations), atmosphere/water treatment (disinfection), antibiofouling materials and in photodynamic therapy of cancer. In this paper, (1)O(2) photosensitizing materials containing the dyes tris(4,4'-diphenyl-2,2'-bipyridine)ruthenium(II) (1, RDB(2+)) or tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) (2, RDP(2+)), immobilized on porous silicone (abbreviated RDB/pSil and RDP/pSil), have been produced and tested for waterborne Enterococcus faecalis inactivation using a laboratory solar simulator and a compound parabolic collector (CPC)-based solar photoreactor. In order to investigate the feasibility of its reuse, the sunlight-exposed RDP/pSil sensitizing material (RDP/pSil-a) has been reloaded with RDP(2+) (RDP/pSil-r). Surprisingly, results for bacteria inactivation with the reloaded material have demonstrated a 4-fold higher efficiency compared to those of either RDP/pSil-a, unused RDB/pSil and the original RDP/pSil. Surface and bulk photochemical characterization of the new material (RDP/pSil-r) has shown that the bactericidal efficiency enhancement is due to aggregation of the silicone-supported photosensitizer on the surface of the polymer, as evidenced by confocal fluorescence lifetime imaging microscopy (FLIM). Photogenerated (1)O(2) lifetimes in the wet sensitizer-doped silicone have been determined to be ten times longer than in water. These facts, together with the water rheology in the solar reactor and the interfacial production of the biocidal species, account for the more effective disinfection observed with the reloaded photosensitizing material. These results extend and improve the operational lifetime of photocatalytic materials for point-of-use (1)O(2)-mediated solar water disinfection.

  13. Influence of oxygen partial pressure on defect concentrations and on oxygen diffusion in UO2+x

    International Nuclear Information System (INIS)

    Pizzi, Elisabetta

    2013-01-01

    The hyper-stoichiometric uranium dioxide (UO 2+x ) is stable over a wide range of temperature and compositions. Such variations of composition and the eventual presence of doping elements or impurities lead to a variation of anionic and electronic defect concentrations. Moreover, many properties of this material are affected by its composition modifications, in particular their atomic transport properties. Firstly we developed a point defect model to evaluate the dependence of the electronic and oxygen defect concentrations upon temperature, equilibrium oxygen partial pressure and impurity content. The physical constants of the model, in particular the equilibrium constants of the defect formation reactions were determined from deviation from stoichiometry and electrical conductivity measurements of literature. This work enabled us to interpret our measures of conductivity, oxygen chemical and self- diffusion coefficients. From a quantitative standpoint, the analysis of our experimental results allows to evaluate the oxygen interstitial diffusion coefficient but also its formation energy. Moreover, an estimate of oxygen di-interstitial formation energy is also provided. Presence of oxygen clusters leads oxygen self- and chemical diffusion to decrease. X-ray Absorption Spectroscopy characterization shows the presence of the same defect in the entire deviation from stoichiometry studied, confirming the approach used to develop the model. (author) [fr

  14. Effects of ambient oxygen concentration on soot temperature and concentration for biodiesel and diesel spray combustion

    KAUST Repository

    Zhang, Ji

    2015-06-01

    Ambient oxygen concentration, a key variable directly related to exhaust gas recirculation (EGR) levels in diesel engines, plays a significant role in particulate matter (PM) and nitrogen oxides (NOx) emissions. The utilization of biodiesel in diesel engines has been investigated over the last decades for its renewable characteristics and lower emissions compared to diesel. In an earlier work, we demonstrated that the soot temperature and concentration of biodiesel were lower than diesel under regular diesel engine conditions without EGR. Soot concentration was quantified by a parameter called KL factor. As a continuous effort, this paper presents an experimental investigation of the ambient oxygen concentration on soot temperature and KL factor during biodiesel and diesel spray combustion. The experiment was implemented in a constant volume chamber system, where the ambient oxygen concentration varied from 21 to 10% and the ambient temperature was kept to 1,000 K. A high speed two-color pyrometry technique was used to measure transient soot temperature and the KL factor of the spray flame. The soot temperature of biodiesel is found to be lower than that of diesel under the same conditions, which follows the same trend from our previous results found when the ambient temperature changes to 21% oxygen conditions. A reduction in ambient oxygen concentration generally reduces the soot temperature for both fuels. However, this is a complicated effect on soot processes as the change of oxygen concentration greatly affects the balance between soot formation and oxidation. The KL factor is observed to be the highest at 12% O2 for diesel and 18% O2 for biodiesel, respectively. On the other hand, the 10% O2 condition shows the lowest KL factor for both fuels. These results can provide quantitative experimental evidences to optimize the ambient oxygen concentration for diesel engines using different fuels for better emissions characteristics. © 2014 American Society of

  15. Comparison of portable oxygen concentrators in a simulated airplane environment.

    Science.gov (United States)

    Fischer, Rainald; Wanka, Eva R; Einhaeupl, Franziska; Voll, Klaus; Schiffl, Helmut; Lang, Susanne M; Gruss, Martin; Ferrari, Uta

    2013-01-01

    Portable oxygen concentrators (POC) are highly desirable for patients with lung disease traveling by airplane, as these devices allow theoretically much higher travel times if additional batteries can be used. However, it is unclear whether POCs produce enough oxygen in airplanes at cruising altitude, even if complying with aviation regulations. We evaluated five frequently used POCs (XPO2 (Invacare, USA), Freestyle (AirSep C., USA), Evergo (Philipps Healthcare, Germany), Inogen One (Inogen, USA), Eclipse 3 (Sequal, USA)) at an altitude of 2650 m (as simulated airplane environment) in 11 patients with chronic obstructive lung disease (COPD) and compared theses POCs with the standard oxygen system (WS120, EMS Ltd., Germany) used by Lufthansa. Oxygen was delivered by each POC for 30 min to each patient at rest, blood gases were then drawn from the arterialized ear lobe. All POCs were able to deliver enough oxygen to increase the PaO(2) of our subjects by at least 1.40 kPa (10 mmHg). However, to achieve this increase, the two most lightweight POCs (Freestyle and Invacare XPO2) had to be run at their maximum level. This causes a significant reduction of battery life. The three other POCs (EverGo, Inogen One, Eclipse 3) and the WS120 were able to increase the PaO(2) by more than 2.55 kPa (20 mmHg), which provides extra safety for patients with more severe basal hypoxemia. When choosing the right oxygen system for air travel in patients in COPD, not only weight, but also battery life and maximum possible oxygen output must be considered carefully. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Hydrogen and oxygen concentrations in IXCs: A compilation

    International Nuclear Information System (INIS)

    Liljegren, L.M.; Terrones, G.T.; Melethil, P.K.

    1996-06-01

    This paper contains four reports and two internal letters that address the estimation of hydrogen and oxygen concentrations in ion exchange columns that treat the water of the K-East and K-West Basins at Hanford. The concern is the flammability of this mixture of gases and planning for safe transport during decommissioning. A transient will occur when the hydrogen filter is temporarily blocked by a sandbag. Analyses are provided for steady-state, transients, and for both wet and dry resins

  17. Effects of ambient oxygen concentration on soot temperature and concentration for biodiesel and diesel spray combustion

    KAUST Repository

    Zhang, Ji; Jing, Wei; Roberts, William L.; Fang, Tiegang

    2015-01-01

    during biodiesel and diesel spray combustion. The experiment was implemented in a constant volume chamber system, where the ambient oxygen concentration varied from 21 to 10% and the ambient temperature was kept to 1,000 K. A high speed two-color

  18. [Relationship among the Oxygen Concentration, Reactive Oxygen Species and the Biological Characteristics of Mouse Bone Marrow Hematopoietic Stem Cells].

    Science.gov (United States)

    Ren, Si-Hua; He, Yu-Xin; Ma, Yi-Ran; Jin, Jing-Chun; Kang, Dan

    2016-02-01

    To investigate the effects of oxygen concentration and reactive oxygen species (ROS) on the biological characteristics of hematopoietic stem cells (HSC) and to analyzed the relationship among the oxygen concentration, ROS and the biological characteristics of mouse HSC through simulation of oxygen environment experienced by PB HSC during transplantation. The detection of reactive oxygen species (ROS), in vitro amplification, directional differentiation (BFU-E, CFU-GM, CFU-Mix), homing of adhesion molecules (CXCR4, CD44, VLA4, VLA5, P-selectin), migration rate, CFU-S of NOD/SCID mice irradiated with sublethal dose were performed to study the effect of oxgen concentration and reactive oxygen species on the biological characteristics of mouse BM-HSC and the relationship among them. The oxygen concentrations lower than normal oxygen concentration (especially hypoxic oxygen environment) could reduce ROS level and amplify more Lin(-) c-kit(+) Sca-1(+) BM HSC, which was more helpful to the growth of various colonies (BFU-E, CFU-GM, CFU-Mix) and to maintain the migratory ability of HSC, thus promoting CFU-S growth significantly after the transplantation of HSC in NOD/SCID mice irradiated by a sublethal dose. BM HSC exposed to oxygen environments of normal, inconstant oxygen level and strenuously thanging of oxygen concentration could result in higher level of ROS, at the same time, the above-mentioned features and functional indicators were relatively lower. The ROS levels of BM HSC in PB HSCT are closely related to the concentrations and stability of oxygen surrounding the cells. High oxygen concentration results in an high level of ROS, which is not helpful to maintain the biological characteristics of BM HSC. Before transplantation and in vitro amplification, the application of antioxidancs and constant oxygen level environments may be beneficial for transplantation of BMMSC.

  19. Mapping oxygen concentration in the awake mouse brain

    Science.gov (United States)

    Lyons, Declan G; Parpaleix, Alexandre; Roche, Morgane; Charpak, Serge

    2016-01-01

    Although critical for brain function, the physiological values of cerebral oxygen concentration have remained elusive because high-resolution measurements have only been performed during anesthesia, which affects two major parameters modulating tissue oxygenation: neuronal activity and blood flow. Using measurements of capillary erythrocyte-associated transients, fluctuations of oxygen partial pressure (Po2) associated with individual erythrocytes, to infer Po2 in the nearby neuropil, we report the first non-invasive micron-scale mapping of cerebral Po2 in awake, resting mice. Interstitial Po2 has similar values in the olfactory bulb glomerular layer and the somatosensory cortex, whereas there are large capillary hematocrit and erythrocyte flux differences. Awake tissue Po2 is about half that under isoflurane anesthesia, and within the cortex, vascular and interstitial Po2 values display layer-specific differences which dramatically contrast with those recorded under anesthesia. Our findings emphasize the importance of measuring energy parameters non-invasively in physiological conditions to precisely quantify and model brain metabolism. DOI: http://dx.doi.org/10.7554/eLife.12024.001 PMID:26836304

  20. Bulk manufacture of concentrated oxygen gas-filled microparticles for intravenous oxygen delivery.

    Science.gov (United States)

    Kheir, John N; Polizzotti, Brian D; Thomson, Lindsay M; O'Connell, Daniel W; Black, Katherine J; Lee, Robert W; Wilking, James N; Graham, Adam C; Bell, David C; McGowan, Francis X

    2013-08-01

    Self-assembling, concentrated, lipid-based oxygen microparticles (LOMs) have been developed to administer oxygen gas when injected intravenously, preventing organ injury and death from systemic hypoxemia in animal models. Distinct from blood substitutes, LOMs are a one-way oxygen carrier designed to rescue patients who experience life-threatening hypoxemia, as caused by airway obstruction or severe lung injury. Here, we describe methods to manufacture large quantities of LOMs using an in-line, recycling, high-shear homogenizer, which can create up to 4 liters of microparticle emulsion in 10 minutes, with particles containing a median diameter of 0.93 microns and 60 volume% of gas phase. Using this process, we screen 30 combinations of commonly used excipients for their ability to form stable LOMs. LOMs composed of DSPC and cholesterol in a 1:1 molar ratio are stable for a 100 day observation period, and the number of particles exceeding 10 microns in diameter does not increase over time. When mixed with blood in vitro, LOMs fully oxygenate blood within 3.95 seconds of contact, and do not cause hemolysis or complement activation. LOMs can be manufactured in bulk by high shear homogenization, and appear to have a stability and size profile which merit further testing. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Automatic measuring device for atomic oxygen concentrations (1962); Dispositif de mesure automatique de concentrations d'oxygene atomique (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Weill, J; Deiss, M; Mercier, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1962-07-01

    Within the framework of the activities of the Autonomous Reactor Electronics Section we have developed a device, which renders automatic one type of measurement carried out in the Physical Chemistry Department at the Saclay Research Centre. We define here: - the physico-chemical principle of the apparatus which is adapted to the measurement of atomic oxygen concentrations; - the physical principle of the automatic measurement; - the properties, performance, constitution, use and maintenance of the automatic measurement device. It is concluded that the principle of the automatic device, whose tests have confirmed the estimation of the theoretical performance, could usefully be adapted to other types of measurement. (authors) [French] Dans le cadre des activites de la Section Autonome d'Electronique des Reacteurs, il a ete realise et mis au point un dispositif permettant de rendre automatique un type de mesures effectuees au Departement de Physico-Chimie du C.E.N. SACLAY. On definit ici: - le principe physico-chimique de l'appareillage, adapte a la mesure de concentrations de l'oxygene atomique; - le principe physique de la mesure automatique; - les qualites, performances, constitution, utilisation, et maintenance du dispositif de mesure automatique. Il est porte en conclusion, que le principe du dispositif automatique realise, dont les essais ont sensiblement confirme l'evaluation des performances theoriques, pourrait etre utilement adapte a d'autres types de mesures courantes. (auteurs)

  2. Numerical modelling of pyrolysis in normal and reduced oxygen concentration

    International Nuclear Information System (INIS)

    Kacem, Ahmed

    2016-01-01

    The predictive capability of computational fluid dynamics (CFD) fire models depends on the accuracy with which the source term due to fuel pyrolysis can be determined. The pyrolysis rate is a key parameter controlling fire behavior, which in turn drives the heat feedback from the flame to the fuel surface. In the present study an in-depth pyrolysis model of a semi-transparent solid fuel (here, clear polymethyl methacrylate or PMMA) with spectrally-resolved radiation and a moving gas/solid interface was coupled with the CFD code ISIS of the IRSN which included turbulence, combustion and radiation for the gas phase. A combined genetic algorithm/pyrolysis model was used with Cone Calorimeter data from a pure pyrolysis experiment to estimate a unique set of kinetic parameters for PMMA pyrolysis. In order to validate the coupled model, ambient air flaming experiments were conducted on square slabs of PMMA with side lengths of 10, 20 and 40 cm. From measurements at the center of the slab, it was found that i) for any sample size, the experimental regression rate becomes almost constant with time, and ii) although the radiative and total heat transfers increase significantly with the sample size, the radiative contribution to the total heat flux remains almost constant (∼80%). Coupled model results show a fairly good agreement with the literature and with current measurements of the heat fluxes, gas temperature and regressing surface rate at the center of the slabs. Discrepancies between predicted and measured total pyrolysis rate are observed, which result from the underestimation of the flame heat flux feedback at the edges of the slab, as confirmed by the comparison between predicted and observed topography of burned samples. Predicted flame heights based on a threshold temperature criterion were found to be close to those deduced from the correlation of Heskestad. Finally, in order to predict the pyrolysis of PMMA under reduced ambient oxygen concentration, a two

  3. A prototype of an electric-discharge gas flow oxygen−iodine laser: I. Modeling of the processes of singlet oxygen generation in a transverse cryogenic slab RF discharge

    International Nuclear Information System (INIS)

    Vagin, N. P.; Ionin, A. A.; Kochetov, I. V.; Napartovich, A. P.; Sinitsyn, D. V.; Yuryshev, N. N.

    2017-01-01

    The existing kinetic model describing self-sustained and electroionization discharges in mixtures enriched with singlet oxygen has been modified to calculate the characteristics of a flow RF discharge in molecular oxygen and its mixtures with helium. The simulations were performed in the gas plug-flow approximation, i.e., the evolution of the plasma components during their motion along the channel was represented as their evolution in time. The calculations were carried out for the O 2 : He = 1: 0, 1: 1, 1: 2, and 1: 3 mixtures at an oxygen partial pressure of 7.5 Torr. It is shown that, under these conditions, volumetric gas heating in a discharge in pure molecular oxygen prevails over gas cooling via heat conduction even at an electrode temperature as low as ~100 K. When molecular oxygen is diluted with helium, the behavior of the gas temperature changes substantially: heat removal begins to prevail over volumetric gas heating, and the gas temperature at the outlet of the discharge zone drops to ~220–230 K at room gas temperature at the inlet, which is very important in the context of achieving the generation threshold in an electric-discharge oxygen−iodine laser based on a slab cryogenic RF discharge.

  4. A prototype of an electric-discharge gas flow oxygen−iodine laser: I. Modeling of the processes of singlet oxygen generation in a transverse cryogenic slab RF discharge

    Energy Technology Data Exchange (ETDEWEB)

    Vagin, N. P.; Ionin, A. A., E-mail: aion@sci.lebedev.ru; Kochetov, I. V.; Napartovich, A. P.; Sinitsyn, D. V., E-mail: dsinit@sci.lebedev.ru; Yuryshev, N. N. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2017-03-15

    The existing kinetic model describing self-sustained and electroionization discharges in mixtures enriched with singlet oxygen has been modified to calculate the characteristics of a flow RF discharge in molecular oxygen and its mixtures with helium. The simulations were performed in the gas plug-flow approximation, i.e., the evolution of the plasma components during their motion along the channel was represented as their evolution in time. The calculations were carried out for the O{sub 2}: He = 1: 0, 1: 1, 1: 2, and 1: 3 mixtures at an oxygen partial pressure of 7.5 Torr. It is shown that, under these conditions, volumetric gas heating in a discharge in pure molecular oxygen prevails over gas cooling via heat conduction even at an electrode temperature as low as ~100 K. When molecular oxygen is diluted with helium, the behavior of the gas temperature changes substantially: heat removal begins to prevail over volumetric gas heating, and the gas temperature at the outlet of the discharge zone drops to ~220–230 K at room gas temperature at the inlet, which is very important in the context of achieving the generation threshold in an electric-discharge oxygen−iodine laser based on a slab cryogenic RF discharge.

  5. Effects of the Oxygenation level on Formation of Different Reactive Oxygen Species During Photodynamic Therapy

    OpenAIRE

    Price, Michael; Heilbrun, Lance; Kessel, David

    2013-01-01

    We examined the effect of the oxygenation level on efficacy of two photosensitizing agents, both of which target lysosomes for photodamage but via different photochemical pathways. Upon irradiation, the chlorin termed NPe6 forms singlet oxygen in high yield while the bacteriopheophorbide WST11 forms only oxygen radicals (in an aqueous environment). Photokilling efficacy by WST11 in cell culture was impaired when the atmospheric oxygen concentration was reduced from 20% to 1%, while photokilli...

  6. Use of an oxygen concentrator in a Nigerian neonatal unit: economic implications and reliability.

    Science.gov (United States)

    Mokuolu, Olugbenga A; Ajayi, Oluade A

    2002-09-01

    A 3-year experience of using an oxygen concentrator in a Nigerian newborn unit and economic appraisal of its effectiveness is reported. The oxygen concentrator is a device that absorbs nitrogen from ambient air, with a resultant oxygen concentration of 85 to 95% at different flow rates. The oxygen concentrator met our oxygen needs which averaged 18 hours a day, and had a huge cost advantage over the oxygen cylinders. The cost of oxygen via cylinder for just one patient for a year exceeds the initial capital outlay for a concentrator. The Puritan-Bennett oxygen concentrator has a lifespan of at least 7 years and is virtually maintenance-free for the 1st 26,400 hours of use, after which some major components might need replacement. We conclude that in developing countries oxygen concentrators are a more cost-effective, reliable and convenient means of oxygen supply than oxygen cylinders, and recommend their use where there is a high demand for oxygen.

  7. Ammonium and nitrite oxidation at nanomolar oxygen concentrations in oxygen minimum zone waters.

    Science.gov (United States)

    Bristow, Laura A; Dalsgaard, Tage; Tiano, Laura; Mills, Daniel B; Bertagnolli, Anthony D; Wright, Jody J; Hallam, Steven J; Ulloa, Osvaldo; Canfield, Donald E; Revsbech, Niels Peter; Thamdrup, Bo

    2016-09-20

    A major percentage of fixed nitrogen (N) loss in the oceans occurs within nitrite-rich oxygen minimum zones (OMZs) via denitrification and anammox. It remains unclear to what extent ammonium and nitrite oxidation co-occur, either supplying or competing for substrates involved in nitrogen loss in the OMZ core. Assessment of the oxygen (O2) sensitivity of these processes down to the O2 concentrations present in the OMZ core (Chile at manipulated O2 levels between 5 nmol⋅L(-1) and 20 μmol⋅L(-1) Rates of both processes were detectable in the low nanomolar range (5-33 nmol⋅L(-1) O2), but demonstrated a strong dependence on O2 concentrations with apparent half-saturation constants (Kms) of 333 ± 130 nmol⋅L(-1) O2 for ammonium oxidation and 778 ± 168 nmol⋅L(-1) O2 for nitrite oxidation assuming one-component Michaelis-Menten kinetics. Nitrite oxidation rates, however, were better described with a two-component Michaelis-Menten model, indicating a high-affinity component with a Km of just a few nanomolar. As the communities of ammonium and nitrite oxidizers were similar to other OMZs, these kinetics should apply across OMZ systems. The high O2 affinities imply that ammonium and nitrite oxidation can occur within the OMZ core whenever O2 is supplied, for example, by episodic intrusions. These processes therefore compete with anammox and denitrification for ammonium and nitrite, thereby exerting an important control over nitrogen loss.

  8. Influence of oxygen concentration on ethylene removal using dielectric barrier discharge

    Science.gov (United States)

    Takahashi, Katsuyuki; Motodate, Takuma; Takaki, Koichi; Koide, Shoji

    2018-01-01

    Ethylene gas is decomposed using a dielectric barrier discharge plasma reactor for long-period preservation of fruits and vegetables. The oxygen concentration in ambient gas is varied from 2 to 20% to simulate the fruit and vegetable transport container. The experimental results show that the efficiency of ethylene gas decomposition increases with decreasing oxygen concentration. The reactions of ethylene molecules with ozone are analyzed by Fourier transform infrared spectrometry. The analysis results show that the oxidization process by ozone is later than that by oxygen atoms. The amount of oxygen atoms that contribute to ethylene removal increases with decreasing oxygen concentration because the reaction between oxygen radicals and oxygen molecules is suppressed at low oxygen concentrations. Ozone is completely removed and the energy efficiency of C2H4 removal is increased using manganese dioxide as a catalyst.

  9. Evaluation of the Oxygen Concentrator Prototypes: Pressure Swing Adsorption Prototype and Electrochemical Prototype

    Science.gov (United States)

    Gilkey, Kelly M.; Olson, Sandra L.

    2015-01-01

    An oxygen concentrator is needed to provide enriched oxygen in support of medical contingency operations for future exploration human spaceflight programs. It would provide continuous oxygen to an ill or injured crew member in a closed cabin environment. Oxygen concentration technology is being pursued to concentrate oxygen from the ambient environment so oxygen as a consumable resource can be reduced. Because oxygen is a critical resource in manned spaceflight, using an oxygen concentrator to pull oxygen out of the ambient environment instead of using compressed oxygen can provide better optimization of resources. The overall goal of this project is to develop an oxygen concentrator module that minimizes the hardware mass, volume, and power footprint while still performing at the required clinical capabilities. Should a medical event occur that requires patient oxygenation, the release of 100 percent oxygen into a small closed cabin environment can rapidly raise oxygen levels to the vehicles fire limit. The use of an oxygen concentrator to enrich oxygen from the ambient air and concentrate it to the point where it can be used for medical purposes means no oxygen is needed from the ultra-high purity (99.5+% O2) oxygen reserve tanks. By not adding oxygen from compressed tanks to the cabin environment, oxygen levels can be kept below the vehicle fire limit thereby extending the duration of care provided to an oxygenated patient without environmental control system intervention to keep the cabin oxygen levels below the fire limits. The oxygen concentrator will be a Food and Drug Administration (FDA) clearable device. A demonstration unit for the International Space Station (ISS) is planned to verify the technology and provide oxygen capability. For the ISS, the demonstration unit should not exceed 10 kg (approximately 22 lb), which is the soft stowage mass limit for launch on resupply vehicles for the ISS. The unit's size should allow for transport within the

  10. Determination of the Minimal Fresh Gas Flow to Maintain a Therapeutic Inspired Oxygen Concentration in a Semi-Closed Anesthesia Circle System Using an Oxygen Concentrator as the Oxygen Source

    National Research Council Canada - National Science Library

    Grano, Joan

    2001-01-01

    The purpose of this study was to determine the rate of oxygen dilution, resulting from argon accumulation, using 3 low fresh gas flow rates using an oxygen concentrator in a semi-closed anesthesia circle system...

  11. Relationship between oxygen concentration, respiration and filtration rate in blue mussel Mytilus edulis

    Science.gov (United States)

    Tang, Baojun; Riisgård, Hans Ulrik

    2018-03-01

    The large water-pumping and particle-capturing gills of the filter-feeding blue mussel Mytilus edulis are oversized for respiratory purposes. Consequently, the oxygen uptake rate of the mussel has been suggested to be rather insensitive to decreasing oxygen concentrations in the ambient water, since the diffusion rate of oxygen from water flowing through the mussel determines oxygen uptake. We tested this hypothesis by measuring the oxygen uptake in mussels exposed to various oxygen concentrations. These concentrations were established via N2-bubbling of the water in a respiration chamber with mussels fed algal cells to stimulate fully opening of the valves. It was found that mussels exposed to oxygen concentrations decreasing from 9 to 2 mg O2/L resulted in a slow but significant reduction in the respiration rate, while the filtration rate remained high and constant. Thus, a decrease of oxygen concentration by 78% only resulted in a 25% decrease in respiration rate. However, at oxygen concentrations below 2 mg O2/L M. edulis responded by gradually closing its valves, resulting in a rapid decrease of filtration rate, concurrent with a rapid reduction of respiration rate. These observations indicated that M. edulis is no longer able to maintain its normal aerobic metabolism at oxygen concentration below 2 mg O2/L, and there seems to be an energy-saving mechanism in bivalve molluscs to strongly reduce their activity when exposed to low oxygen conditions.

  12. Comparison of domiciliary oxygen using liquid oxygen and concentrator in northern Taiwan

    Directory of Open Access Journals (Sweden)

    Chien-Ling Su

    2014-01-01

    Conclusion: Patients in the LOG used oxygen for longer hours, went on more outings, and were more likely to travel with oxygen than patients in the OCG. Being ambulatory with liquid oxygen might enable patients with COPD to walk more effectively.

  13. [Effect of different oxygen concentrations on biological properties of bone marrow hematopoietic stem cells of mice].

    Science.gov (United States)

    Ma, Yi-Ran; Ren, Si-Hua; He, Yu-Xin; Wang, Lin-Lin; Jin, Li; Hao, Yi-Wen

    2012-10-01

    This study purposed to investigate the effects of different oxygen concentrations and reactive oxygen species (ROS) on the biological characteristics of hematopoietic stem cells (HSC) and their possible mechanisms through simulating oxygen environment to which the peripheral blood HSC are subjected in peripheral blood HSCT. The proliferation ability, cell cycle, directed differentiation ability, ROS level and hematopoietic reconstitution ability of Lin(-)c-kit(+)Sca-1(+) BMHSC were detected by using in vitro amplification test, directional differentiation test, cell cycle analysis, ROS assay and transplantation of Lin(-)c-kit(+)Sca-1(+) HSC from sublethally irradiated mice respectively. The results showed that oxygen concentrations lower than normal oxygen concentration, especially in hypoxic oxygen environment, could reduce ROS generation and amplify more primitive CD34(+)AC133(+) HSC and active CD34(+) HSC, and maintain more stem cells in the G(0)/G(1) phase, which is more helpful to the growth of CFU-S and viability of mice. At the same time, BMHSC exposed to normal oxygen level or inconstant and greatly changed oxygen concentrations could produce a high level of ROS, and the above-mentioned features and functional indicators are relatively low. It is concluded that ROS levels of HSC in BMHSCT are closely related with the oxygen concentration surrounding the cells and its stability. Low oxygen concentration and antioxidant intervention are helpful to transplantation of BMHSC.

  14. Introduction of high oxygen concentrations into silicon wafers by high-temperature diffusion

    International Nuclear Information System (INIS)

    Casse, G.; Glaser, M.; Lemeilleur, F.; Ruzin, A.; Wegrzecki, M.

    1999-01-01

    The tolerance of silicon detectors to hadron irradiation can be improved by the introduction of a high concentration of oxygen into the starting material. High-resistivity Floating-Zone (FZ) silicon is required for detectors used in particle physics applications. A significantly high oxygen concentration (>10 17 atoms cm -3 ) cannot readily be achieved during the FZ silicon refinement. The diffusion of oxygen at elevated temperatures from a SiO 2 layer grown on both sides of a silicon wafer is a simple and effective technique to achieve high and uniform concentrations of oxygen throughout the bulk of a 300 μm thick silicon wafer

  15. Characterization of reaction products in sodium-oxygen batteries : An electrolyte concentration study

    OpenAIRE

    Hedman, Jonas

    2017-01-01

    In this thesis, the discharge products formed at the cathode and the performance and cell chemistry of sodium-oxygen batteries have been studied. This was carried out using different NaOTf salt concentrations. The influence of different salt concentrations on sodium-oxygen batteries was investigated since it has been shown that increasing the salt concentration beyond conventional concentrations could result in advantages such as increased stability of the electrolytes towards decomposition, ...

  16. Correlation of Oxygenated Hemoglobin Concentration and Psychophysical Amount on Speech Recognition

    Science.gov (United States)

    Nozawa, Akio; Ide, Hideto

    The subjective understanding on oral language understanding task is quantitatively evaluated by the fluctuation of oxygenated hemoglobin concentration measured by the near-infrared spectroscopy. The English listening comprehension test wihch consists of two difficulty level was executed by 4 subjects during the measurement. A significant correlation was found between the subjective understanding and the fluctuation of oxygenated hemoglobin concentration.

  17. About Error in Measuring Oxygen Concentration by Solid-Electrolyte Sensors

    Directory of Open Access Journals (Sweden)

    V. I. Nazarov

    2008-01-01

    Full Text Available The paper evaluates additional errors while measuring oxygen concentration in a gas mixture by a solid-electrolyte cell. Experimental dependences of additional errors caused by changes in temperature in a sensor zone, discharge of gas mixture supplied to a sensor zone, partial pressure in the gas mixture and fluctuations in oxygen concentrations in the air.

  18. The dynamics of dissolved oxygen concentration for water quality monitoring and assessment in polder ditches

    NARCIS (Netherlands)

    Veeningen, R.

    1983-01-01

    This study deals with the use of the dynamics of dissolved oxygen concentration for water quality assessment in polder ditches. The dynamics of the dissolved oxygen concentration, i.e. the temporal and spatial variations in a few polder ditches under a range of natural, pollution and management

  19. Monitor hemoglobin concentration and oxygen saturation in living mouse tail using photoacoustic CT scanner

    Science.gov (United States)

    Liu, Bo; Kruger, Robert; Reinecke, Daniel; Stantz, Keith M.

    2010-02-01

    Purpose: The purpose of this study is to use PCT spectroscopy scanner to monitor the hemoglobin concentration and oxygen saturation change of living mouse by imaging the artery and veins in a mouse tail. Materials and Methods: One mouse tail was scanned using the PCT small animal scanner at the isosbestic wavelength (796nm) to obtain its hemoglobin concentration. Immediately after the scan, the mouse was euthanized and its blood was extracted from the heart. The true hemoglobin concentration was measured using a co-oximeter. Reconstruction correction algorithm to compensate the acoustic signal loss due to the existence of bone structure in the mouse tail was developed. After the correction, the hemoglobin concentration was calculated from the PCT images and compared with co-oximeter result. Next, one mouse were immobilized in the PCT scanner. Gas with different concentrations of oxygen was given to mouse to change the oxygen saturation. PCT tail vessel spectroscopy scans were performed 15 minutes after the introduction of gas. The oxygen saturation values were then calculated to monitor the oxygen saturation change of mouse. Results: The systematic error for hemoglobin concentration measurement was less than 5% based on preliminary analysis. Same correction technique was used for oxygen saturation calculation. After correction, the oxygen saturation level change matches the oxygen volume ratio change of the introduced gas. Conclusion: This living mouse tail experiment has shown that NIR PCT-spectroscopy can be used to monitor the oxygen saturation status in living small animals.

  20. Oxygen concentration diffusion analysis of lead-bismuth-cooled, natural-circulation reactor

    International Nuclear Information System (INIS)

    Ito, Kei; Sakai, Takaaki

    2001-11-01

    The feasibility study on fast breeder reactors in Japan has been conducted at JNC and related organizations. The Phase-I study has finished in March, 2001. During the Phase-I activity, lead-bismuth eutectic coolant has been selected as one of the possible coolant options and a medium-scale plant, cooled by a lead-bismuth natural circulation flow was studied. On the other side, it is known that lead-bismuth eutectic has a problem of structural material corrosiveness. It was found that oxygen concentration control in the eutectic plays an important role on the corrosion protection. In this report, we have developed a concentration diffusion analysis code (COCOA: COncentration COntrol Analysis code) in order to carry out the oxygen concentration control analysis. This code solves a two-dimensional concentration diffusion equation by the finite differential method. It is possible to simulate reaction of oxygen and hydrogen by the code. We verified the basic performance of the code and carried out oxygen concentration diffusion analysis for the case of an oxygen increase by a refueling process in the natural circulation reactor. In addition, characteristics of the oxygen control system was discussed for a different type of the control system as well. It is concluded that the COCOA code can simulate diffusion of oxygen concentration in the reactor. By the analysis of a natural circulation medium-scale reactor, we make clear that the ON-OFF control and PID control can well control oxygen concentration by choosing an appropriate concentration measurement point. In addition, even when a trouble occurs in the oxygen emission or hydrogen emission system, it observes that control characteristic drops away. It is still possible, however, to control oxygen concentration in such case. (author)

  1. Singlet Ground State Magnetism:

    DEFF Research Database (Denmark)

    Loidl, A.; Knorr, K.; Kjems, Jørgen

    1979-01-01

    The magneticGamma 1 –Gamma 4 exciton of the singlet ground state system TbP has been studied by inelastic neutron scattering above the antiferromagnetic ordering temperature. Considerable dispersion and a pronounced splitting was found in the [100] and [110] directions. Both the band width...

  2. Radiosensitivity of Hela cells in various O2 concentrations and consideration of oxygen effect in radiotherapy

    International Nuclear Information System (INIS)

    Kuroda, Yoshikazu; Nyunoya, Koichiro

    1979-01-01

    The aim of this paper is the study of the radiosensitivity of HeLa cells in vitro in various oxygen concentrations and the consideration of the utilization of oxygen effect in radiation therapy, based on the data of HeLa cells and tumor oxygen tension. Survival curves of HeLa cells are found to be exponential as a function of radiation dose and the radiosensitivity is dependent on oxygen tension of culture medium. Relative radiosensitivity decreases remarkably at low level of oxygen, especially under 9 mmHg pO 2 . The utilization of oxygen effect in radiation may be useful in hyperbaric oxygen inhalation and not useful under local tissue hypoxia induced by tourniquet application. Reoxygenation occurs with shrinkage of tumor after irradiation and this phenomenon will diminish the value of hyperbaric oxygen in radiation therapy. (author)

  3. Singlet Oxygen Production and Biological Activity of Hexanuclear Chalcocyanide Rhenium Cluster Complexes [{Re(6)Q(8)}(CN)(6)](4-) (Q = S, Se, Te)

    Czech Academy of Sciences Publication Activity Database

    Solovieva, A.O.; Kirakci, Kaplan; Ivanov, A.; Kubát, Pavel; Pozmogova, T.N.; Miroshnichenko, S.M.; Vorontsova, E.V.; Chechushkov, A.V.; Trifonova, K.E.; Fufaeva, M.S.; Kretov, E.I.; Mironov, Y.V.; Poveshchenko, A.F.; Lang, Kamil; Shestopalov, M.A.

    2017-01-01

    Roč. 56, č. 21 (2017), s. 13491-13499 ISSN 0020-1669 R&D Projects: GA ČR(CZ) GA16-15020S Institutional support: RVO:61388980 ; RVO:61388955 Keywords : photophysical properties * silica nanoparticles * molecular-oxygen * iodide cluster * luminescence Subject RIV: CA - Inorganic Chemistry; CF - Physical ; Theoretical Chemistry (UFCH-W) OBOR OECD: Inorganic and nuclear chemistry; Physical chemistry (UFCH-W) Impact factor: 4.857, year: 2016

  4. Small CAB-like proteins prevent formation of singlet oxygen in the damaged photosystem II complex of the cyanobacterium Synechocystis sp PCC 6803

    Czech Academy of Sciences Publication Activity Database

    Sinha, R. K.; Komenda, Josef; Knoppová, Jana; Sedlářová, M.; Pospíšil, P.

    2012-01-01

    Roč. 35, č. 4 (2012), s. 806-818 ISSN 0140-7791 R&D Projects: GA MŠk(CZ) ED2.1.00/03.0110; GA ČR(CZ) GAP501/11/0377 Institutional research plan: CEZ:AV0Z50200510 Keywords : oxidative stress * photoinhibition * reactive oxygen species Subject RIV: EE - Microbiology, Virology Impact factor: 5.135, year: 2012

  5. Oxygen concentrators performance with nitrous oxide at 50:50 volume

    Directory of Open Access Journals (Sweden)

    Jorge Ronaldo Moll

    2014-06-01

    Full Text Available Background and objectives: Few investigations have addressed the safety of oxygen from concentrators for use in anesthesia in association with nitrous oxide. This study evaluated the percent of oxygen from a concentrator in association with nitrous oxide in a semi-closed rebreathing circuit. Methods: Adult patients undergoing low risk surgery were randomly allocated into two groups, receiving a fresh gas flow of oxygen from concentrators (O293 or of oxygen from concentrators and nitrous oxide (O293N2O. The fraction of inspired oxygen and the percentage of oxygen from fresh gas flow were measured every 10 min. The ratio of FiO2/oxygen concentration delivered was compared at various time intervals and between the groups. Results: Thirty patients were studied in each group. There was no difference in oxygen from concentrators over time for both groups, but there was a significant improvement in the FiO2 (p < 0.001 for O293 group while a significant decline (p < 0.001 for O293N2O. The FiO2/oxygen ratio varied in both groups, reaching a plateau in the O293 group. Pulse oximetry did not fall below 98.5% in either group. Conclusion: The FiO2 in the mixture of O293 and nitrous oxide fell during the observation period although oxygen saturation was higher than 98.5% throughout the study. Concentrators can be considered a stable source of oxygen for use during short anesthetic procedures, either pure or in association with nitrous oxide at 50:50 volume.

  6. Influence of variable oxygen concentration on the response of cells to heat or x irradiation

    International Nuclear Information System (INIS)

    Gerweck, L.E.; Richards, B.; Jennings, M.

    1981-01-01

    The influence of oxygen concentration on the lethal response of cells exposed to 43 0 C hyperthermia was determined and compared to the response of cells exposed to radiation under equivalent culturing and environmental conditions. Chinese hamster ovary (CHO) cells were heated or irradiated 0.5 h after induction of hypoxia and then reoxygenated following treatment. The oxygen enhancement ratio (OER) for heat or radiation was determined at the 1% survival level from least-squares fit of survival curves. A maximum OER of 3.1 +- 0.2 was observed in the 20 to 95% oxygen concentration range. The OER for heat, however, was 1.0 +- 0.1 irrespective of the gas-phase oxygen concentration. These results show that the lethal effects of heat are not influenced by the oxygen concentration at the time of treatment in CHO cells exposed to 43 0 C hyperthermia

  7. Effects of the oxygenation level on formation of different reactive oxygen species during photodynamic therapy.

    Science.gov (United States)

    Price, Michael; Heilbrun, Lance; Kessel, David

    2013-01-01

    We examined the effect of the oxygenation level on efficacy of two photosensitizing agents, both of which target lysosomes for photodamage, but via different photochemical pathways. Upon irradiation, the chlorin termed NPe6 forms singlet oxygen in high yield while the bacteriopheophorbide WST11 forms only oxygen radicals (in an aqueous environment). Photokilling efficacy by WST11 in cell culture was impaired when the atmospheric oxygen concentration was reduced from 20% to 1%, while photokilling by NPe6 was unaffected. Studies in a cell-free system revealed that the rates of photobleaching of these agents, as a function of the oxygenation level, were correlated with results described above. Moreover, the rate of formation of oxygen radicals by either agent was more sensitive to the level of oxygenation than was singlet oxygen formation by NPe6. These data indicate that the photochemical process that leads to oxygen radical formation is more dependent on the oxygenation level than is the pathway leading to formation of singlet oxygen. © 2013 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2013 The American Society of Photobiology.

  8. Effect of hyperbaric oxygen therapy combined with autologous platelet concentrate applied in rabbit fibula fraction healing

    Directory of Open Access Journals (Sweden)

    Paulo Cesar Fagundes Neves

    2013-09-01

    Full Text Available OBJECTIVES: The purpose is to study the effects of hyperbaric oxygen therapy and autologous platelet concentrates in healing the fibula bone of rabbits after induced fractures. METHODS: A total of 128 male New Zealand albino rabbits, between 6-8 months old, were subjected to a total osteotomy of the proximal portion of the right fibula. After surgery, the animals were divided into four groups (n = 32 each: control group, in which animals were subjected to osteotomy; autologous platelet concentrate group, in which animals were subjected to osteotomy and autologous platelet concentrate applied at the fracture site; hyperbaric oxygen group, in which animals were subjected to osteotomy and 9 consecutive daily hyperbaric oxygen therapy sessions; and autologous platelet concentrate and hyperbaric oxygen group, in which animals were subjected to osteotomy, autologous platelet concentrate applied at the fracture site, and 9 consecutive daily hyperbaric oxygen therapy sessions. Each group was divided into 4 subgroups according to a pre-determined euthanasia time points: 2, 4, 6, and 8 weeks postoperative. After euthanasia at a specific time point, the fibula containing the osseous callus was prepared histologically and stained with hematoxylin and eosin or picrosirius red. RESULTS: Autologous platelet concentrates and hyperbaric oxygen therapy, applied together or separately, increased the rate of bone healing compared with the control group. CONCLUSION: Hyperbaric oxygen therapy and autologous platelet concentrate combined increased the rate of bone healing in this experimental model.

  9. Synthesis, singlet-oxygen photogeneration, two-photon absorption, photo-induced DNA cleavage and cytotoxic properties of an amphiphilic β-Schiff-base linked Ru(II) polypyridyl–porphyrin conjugate

    International Nuclear Information System (INIS)

    Ke, Hanzhong; Ma, Wanpeng; Wang, Hongda; Cheng, Guoe; Yuan, Han; Wong, Wai-Kwok; Kwong, Daniel W.J.; Tam, Hoi-Lam; Cheah, Kok-Wai; Chan, Chi-Fai; Wong, Ka-Leung

    2014-01-01

    A novel porphyrin–polypyridyl ruthenium(II) conjugate (TPP–Ru), in which the ruthenium(II) polypyridyl moiety is linked to the β-position of the tetraphenylporphyrin via a Schiff base linkage, has been synthesized and characterized by 1 H NMR, HRMS and UV–visible spectroscopy. The relative singlet oxygen quantum yield and two-photon absorption cross-section of this conjugate, together with its photo-induced DNA cleavage and cytotoxic activities were measured. The results show that the amphiphilic ruthenium(II) polypyridyl–porphyrin conjugate is an effective DNA photocleavage agent, with potential application in one- and two-photon absorption anti-cancer photodynamic therapy. - Highlights: • New porphyrin–ruthenium(II) polypyridyl complexes (TTP–Ru) have been synthesized. • The TTP–Ru shows substantial two-photon absorption cross-section (σ 2 =391 GM). • The TTP–Ru exhibits a substantial 1 O 2 quantum yield (0.64±0.13). • The TTP–Ru exhibits a strong DNA cleavage activity upon photo-excitation. • The TTP–Ru is available for in vitro imaging and as a photodynamic therapy agent

  10. Synthesis, singlet-oxygen photogeneration, two-photon absorption, photo-induced DNA cleavage and cytotoxic properties of an amphiphilic β-Schiff-base linked Ru(II) polypyridyl–porphyrin conjugate

    Energy Technology Data Exchange (ETDEWEB)

    Ke, Hanzhong, E-mail: kehanz@163.com [Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan, Hubei 430074 (China); Ma, Wanpeng; Wang, Hongda; Cheng, Guoe [Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan, Hubei 430074 (China); Yuan, Han [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Wong, Wai-Kwok, E-mail: wkwong@hkbu.edu.hk [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Institute of Advanced Materials, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Kwong, Daniel W.J. [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Tam, Hoi-Lam; Cheah, Kok-Wai [Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Institute of Advanced Materials, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Chan, Chi-Fai; Wong, Ka-Leung [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China)

    2014-10-15

    A novel porphyrin–polypyridyl ruthenium(II) conjugate (TPP–Ru), in which the ruthenium(II) polypyridyl moiety is linked to the β-position of the tetraphenylporphyrin via a Schiff base linkage, has been synthesized and characterized by {sup 1}H NMR, HRMS and UV–visible spectroscopy. The relative singlet oxygen quantum yield and two-photon absorption cross-section of this conjugate, together with its photo-induced DNA cleavage and cytotoxic activities were measured. The results show that the amphiphilic ruthenium(II) polypyridyl–porphyrin conjugate is an effective DNA photocleavage agent, with potential application in one- and two-photon absorption anti-cancer photodynamic therapy. - Highlights: • New porphyrin–ruthenium(II) polypyridyl complexes (TTP–Ru) have been synthesized. • The TTP–Ru shows substantial two-photon absorption cross-section (σ{sub 2}=391 GM). • The TTP–Ru exhibits a substantial {sup 1}O{sub 2} quantum yield (0.64±0.13). • The TTP–Ru exhibits a strong DNA cleavage activity upon photo-excitation. • The TTP–Ru is available for in vitro imaging and as a photodynamic therapy agent.

  11. The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT).

    Science.gov (United States)

    Slouka, Christoph; Kainz, Theresa; Navickas, Edvinas; Walch, Gregor; Hutter, Herbert; Reichmann, Klaus; Fleig, Jürgen

    2016-11-22

    The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La 3+ donor-doped, Fe 3+ acceptor-doped and La 3+ /Fe 3+ -co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

  12. The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT

    Directory of Open Access Journals (Sweden)

    Christoph Slouka

    2016-11-01

    Full Text Available The different properties of acceptor-doped (hard and donor-doped (soft lead zirconate titanate (PZT ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La3+ donor-doped, Fe3+ acceptor-doped and La3+/Fe3+-co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

  13. Detection of ultra-low oxygen concentration based on the fluorescence blinking dynamics of single molecules

    Science.gov (United States)

    Wu, Ruixiang; Chen, Ruiyun; Zhou, Haitao; Qin, Yaqiang; Zhang, Guofeng; Qin, Chengbing; Gao, Yan; Gao, Yajun; Xiao, Liantuan; Jia, Suotang

    2018-01-01

    We present a sensitive method for detection of ultra-low oxygen concentrations based on the fluorescence blinking dynamics of single molecules. The relationship between the oxygen concentration and the fraction of time spent in the off-state, stemming from the population and depopulation of triplet states and radical cationic states, can be fitted with a two-site quenching model in the Stern-Volmer plot. The oxygen sensitivity is up to 43.42 kPa-1 in the oxygen partial pressure region as low as 0.01-0.25 kPa, which is seven times higher than that of the fluorescence intensity indicator. This method avoids the limitation of the sharp and non-ignorable fluctuations that occur during the measurement of fluorescence intensity, providing potential applications in the field of low oxygen-concentration monitoring in life science and industry.

  14. Oxygen toxicity

    Directory of Open Access Journals (Sweden)

    C. A. van der Westhuizen

    1990-07-01

    Full Text Available Oxygen has been discovered about 200 years ago. Since then the vital physiological involvement of oxygen in various biologi­cal processes, mainly energy production, has been established. However, in the body molecular oxygen can be converted to toxic oxygen metabolites such as superoxide anion, hydrogen peroxide, the hydroxyl radical and singlet oxygen. These toxic metabolites are produced mainly in the mitochondria, plasma membranes and endoplasmic reticulum.

  15. 75 FR 739 - Use of Additional Portable Oxygen Concentrator Devices on Board Aircraft

    Science.gov (United States)

    2010-01-06

    ...;Prices of new books are listed in the first FEDERAL REGISTER issue of each #0;week. #0; #0; #0; #0;#0... approved by the Food and Drug Administration (FDA) reduce the risks typically associated with compressed... developed small portable oxygen concentrators (POC) that work by separating oxygen from nitrogen and other...

  16. Methane oxidation and formation of EPS in compost: effect of oxygen concentration

    International Nuclear Information System (INIS)

    Wilshusen, J.H.; Hettiaratchi, J.P.A.; Visscher, A. de; Saint-Fort, R.

    2004-01-01

    Oxygen concentration plays an important role in the regulation of methane oxidation and the microbial ecology of methanotrophs. However, this effect is still poorly quantified in soil and compost ecosystems. The effect of oxygen on the formation of exopolymeric substances (EPS) is as yet unknown. We studied the effect of oxygen on the evolution of methanotrophic activity. At both high and low oxygen concentrations, peak activity was observed twice within a period of 6 months. Phospholipid fatty acid analysis showed that there was a shift from type I to type II methanotrophs during this period. At high oxygen concentration, EPS production was about 250% of the amount at low oxygen concentration. It is hypothesized that EPS serves as a carbon cycling mechanism for type I methanotrophs when inorganic nitrogen is limiting. Simultaneously, EPS stimulates nitrogenase activity in type II methanotrophs by creating oxygen-depleted zones. The kinetic results were incorporated in a simulation model for gas transport and methane oxidation in a passively aerated biofilter. Comparison between the model and experimental data showed that, besides acting as a micro-scale diffusion barrier, EPS can act as a barrier to macro-scale diffusion, reducing the performance of such biofilters. - 1.5% oxygen resulted in a slightly higher and more stable methane oxidation activity

  17. Changes in Oxygen Partial Pressure in the Vitreous Body and Arterial Blood of Rabbits Depending on Oxygen Concentration in Inspired Mixture.

    Science.gov (United States)

    Amkhanitskaya, L I; Nikolaeva, G V; Sokolova, N A

    2015-07-01

    We demonstrated that the vitreous body of one-month-old rabbits becomes a "reservoir" for storage and accumulation of oxygen after exposure to additional oxygenation of the organism (O2 concentrations in inspired gas mixture were 40, 60, 85, and 99%). The higher was O2 concentration in inspired mixture, the higher was oxygen saturation of the blood and vitreous body. O2 concentration of 40% was relatively safe for eye tissues. O2 concentration >60% induced oxygen accumulation in the vitreous body, which can be a provoking factor for the development of oxygen-induced pathologies.

  18. Radiation-induced lipid peroxidation: influence of oxygen concentration and membrane lipid composition

    International Nuclear Information System (INIS)

    Wolters, H.; Tilburg, C.A.M. van; Konings, A.W.T.

    1987-01-01

    Radiation -induced lipid peroxidation phospholipid liposomes was investigated in terms of its dependence on lipid composition and oxygen concentration. Non-peroxidizable lipid incorporated in the liposomes reduced the rate of peroxidation of the peroxidizable phospholipid acyl chains, possibly by restricting the length of chain reactions. The latter effect is believed to be caused by interference of the non-peroxidizable lipids in the bilayer. At low oxygen concentration lipid peroxidation was reduced. The cause of this limited peroxidation may be a reduced number of radical initiation reactions possibly involving oxygen-derived superoxide radicals. Killing of proliferating mammalian cells, irradiated at oxygen concentrations ranging from 0 to 100%, appeared to be independent of the concentration of peroxidizable phospholipids in the cell membranes. This indicates that lipid peroxidation is not the determining process in radiation-induced reproductive cell death. (author)

  19. Digitized Onondaga Lake Dissolved Oxygen Concentrations and Model Simulated Values using Bayesian Monte Carlo Methods

    Data.gov (United States)

    U.S. Environmental Protection Agency — The dataset is lake dissolved oxygen concentrations obtained form plots published by Gelda et al. (1996) and lake reaeration model simulated values using Bayesian...

  20. Evaluation of Oxygen Concentrators and Chemical Oxygen Generators at Altitude and Temperature Extremes

    Science.gov (United States)

    2015-04-22

    Current COGs typically contain one or more of the following solid compounds: sodium chlorate , sodium perchlorate, potassium superoxide, or...produces heat. The COGs evaluated in this study are the O2PAK, TraumAid, and BOB. 3.2.1 O2PAK. The main ingredient in the O2PAK is sodium chlorate ...In 1902, the Lancet reported on Kamm’s oxygen generator invention for medical use. The device used chlorate cakes and manganese oxide and, when

  1. The role of changes in the oxygen concentration in modification of reproductive death of cells in vitro

    International Nuclear Information System (INIS)

    Korystov, Yu.N.

    1983-01-01

    In this report the data are discussed and summarized concerning cell oxygenation in culture. Formulae are proposed for calculation of the oxygen concentration in suspension, monolayer and spheroid, as well as numerical parameters are submitted determining the oxygenation of cells in vitro. This permits to estimate quantitatively the oxygen concentration at the cell surface upon irradiation in different experimental conditions

  2. A theoretical evaluation of the oxygen concentration in a corrosion-fatigue crack

    International Nuclear Information System (INIS)

    Turnbull, A.

    1981-01-01

    The oxygen concentration in a corrosion-fatigue crack has been evaluated theoretically by assuming that oxygen was consumed by cathodic reduction on the walls of the crack and mass transport occurred by diffusion and advection (forced convection), with the latter resulting from the sinusoidal variation of the displacement of the crack walls. By using parameters relevant to a compact tension specimen, the time-dependent distribution of the oxygen concentration in the crack was calculated as a function of ΔK (the range of the stress intensity factor), R-value (minimum load/maximum load), frequency, crack length, and electrode potential. The influence of advection was to significantly enhance the mass transport of oxygen in the crack compared with ''diffusion-only'' even at low frequencies and low ΔK. Regions in the crack were identified in which advection dominance or diffusion dominance of the mass transport of oxygen occurred

  3. The effect of inhaling concentrated oxygen on performance during repeated anaerobic exercise

    Directory of Open Access Journals (Sweden)

    J Heller

    2010-09-01

    Full Text Available The objective of the pilot study was to test the effect of inhaling 99.5% oxygen on recovery. The source of concentrated oxygen was O-PUR (Oxyfit. Research subjects completed two thirty-second Wingate tests at an interval of ten minutes, and in the interval between the tests the subjects inhaled either oxygen or a placebo in random order. This procedure was then repeated. The pilot study revealed a significantly (p<0.03 smaller performance drop in the second Wingate test following the inhalation of 99.5% oxygen when compared with the placebo. The results of the study indicate that inhaling concentrated oxygen may have a positive effect on short-term recovery processes.

  4. The influence of oxygen admixture concentration on microdeformation behavior of niobium

    International Nuclear Information System (INIS)

    Ivantsov, V.I.

    2004-01-01

    The microplasticity behavior of solid solutions Nb-O (relative residual deformations ε = 2 centre dot 10 -7 ...10 -4 ) in dependence on oxygen admixture concentration (C = 0,06...1,4 at.% O) was studied. The values of microplastic deformation parameters (precision elastic limit σ E , micro yield stress σ A and elastic module E) of pure niobium and solid solutions Nb-O were determinated. The empiric correlation of dependence σ E and σ A versus oxygen concentration were got. It was discussed the mechanism of oxygen admixture influence on stage nature of microflow and deformation hardening of niobium

  5. Trough Concentrations of Vancomycin in Patients Undergoing Extracorporeal Membrane Oxygenation.

    Directory of Open Access Journals (Sweden)

    So Jin Park

    Full Text Available To investigate the appropriateness of the current vancomycin dosing strategy in adult patients with extracorporeal membrane oxygenation (ECMO, between March 2013 and November 2013, patients who were treated with vancomycin while on ECMO were enrolled. Control group consisted of 60 patients on vancomycin without ECMO, stayed in medical intensive care unit during the same study period and with the same exclusion criteria. Early trough levels were obtained within the fourth dosing, and maintenance levels were measured at steady state. A total of 20 patients were included in the analysis in ECMO group. Sixteen patients received an initial intravenous dose of 1.0 g vancomycin followed by 1.0 g every 12 hours. The non-steady state trough level of vancomycin after starting administration was subtherapeutic in 19 patients (95.00% in ECMO group as compared with 40 patients (66.67% in the control group (p = 0.013. Vancomycin clearance was 1.27±0.51 mL/min/kg, vancomycin clearance/creatinine clearance ratio was 0.90 ± 0.37, and elimination rate constant was 0.12 ± 0.04 h-1. Vancomycin dosingfrequency and total daily dose were significantly increased after clinical pharmacokinetic services of the pharmacist based on calculated pharmacokinetic parameters (from 2.10 ± 0.72 to 2.90 ± 0.97 times/day, p = 0.002 and from 32.54 ± 8.43 to 42.24 ± 14.62mg/kg, p = 0.014 in ECMO group in contrast with those (from 2.11 ± 0.69 to 2.37 ± 0.86 times/day, p = 0.071 and from 33.91 ± 11.85 to 31.61 ± 17.50 mg/kg, p = 0.350 in the control group.Although the elimination rate for vancomycin was similar with population parameter of non ECMO patients, the current dosing strategy of our institution for vancomycinin our ICU was not sufficient to achieve the target trough in the initial period in most patients receiving ECMO.

  6. Fire feedbacks over geological time and the evolution of atmospheric oxygen concentration

    Science.gov (United States)

    Mills, B.; Belcher, C.; Lenton, T. M.

    2017-12-01

    During the 4.5 billion year history of the Earth, the concentration of oxygen in the atmosphere has risen from trace levels to today's 21%. Yet over the last 400 million years, O2 concentration appears to have remained within a relatively narrow range (around 15% - 30%), despite dramatic changes in the nature of global biogeochemical cycling. This stability has been crucial for continued animal evolution, and is thought to have arisen through feedbacks between oxygen, wildfire and plant productivity: the strong oxygen- dependence of fire initiation and spread means that global photosynthetic primary productivity is suppressed when oxygen levels are high, and enhanced when levels are low. We present biogeochemical modelling of the long term carbon and oxygen cycles, which aims to capture the operation of the wildfire feedback alongside other key processes. We find that wildfire can effectively stabilize long term oxygen concentrations, but that the nature of this feedback has changed as plant evolution has provided different fuels. Specifically, the evolution of early angiosperms during the Cretaceous period provided new understory fuels that more easily facilitated crown and canopy fires. Adding these dynamics to our model produces a more stable system over long timescales, and the model predicts that oxygen concentration has declined towards the present day - a prediction that is supported by other independent estimates.

  7. Effects of vacuum suctioning and strategic drape tenting on oxygen concentration in a simulated surgical field.

    Science.gov (United States)

    Kung, Theodore A; Kong, Sarah W; Aliu, Oluseyi; Azizi, Jahan; Kai, Salim; Cederna, Paul S

    2016-02-01

    To investigate the isolated and combined effects of vacuum suctioning and strategic drape tenting on oxygen concentration in an experimental setting. Experimental. Clinical simulation center of a university-affiliated hospital. Mannequin simulation of a patient undergoing facial surgery under sedation anesthesia. Supplemental oxygen was delivered via nasal cannula. Vacuum suctioning and strategic drape tenting. The experimental trials entailed measuring oxygen concentration around the nasal cannula continuously either in the presence or absence of a standard operating room vacuum suction system and strategic tenting of surgical drapes. The primary outcome was the time required for oxygen concentration to reach 21%. In the control group (without suction or strategic tenting), a mean time of 180 seconds elapsed until the measured oxygen concentration reached 21% after cessation of oxygen delivery. Use of a vacuum suction device alone (110 seconds; P strategic tenting (110 seconds; P strategic tenting of surgical drapes has a theoretical benefit to decreasing the pooling of oxygen around the surgical site, further investigation is necessary before its routine use is recommended. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. One year of Seaglider dissolved oxygen concentration profiles at the PAP site

    Science.gov (United States)

    Binetti, Umberto; Kaiser, Jan; Heywood, Karen; Damerell, Gillian; Rumyantseva, Anna

    2015-04-01

    Oxygen is one of the most important variables measured in oceanography, influenced both by physical and biological factors. During the OSMOSIS project, 7 Seagliders were used in 3 subsequent missions to measure a multidisciplinary suite of parameters at high frequency in the top 1000 m of the water column for one year, from September 2012 to September 2013. The gliders were deployed at the PAP time series station (nominally at 49° N 16.5° W) and surveyed the area following a butterfly-shaped path. Oxygen concentration was measured by Aanderaa optodes and calibrated using ship CTD O2 profiles during 5 deployment and recovery cruises, which were in turn calibrated by Winkler titration of discrete samples. The oxygen-rich mixed layer deepens in fall and winter and gets richer in oxygen when the temperature decreases. The spring bloom did not happen as expected, but instead the presence of a series of small blooms was measured throughout spring and early summer. During the summer the mixed layer become very shallow and oxygen concentrations decreased. A Deep Oxygen Maximum (DOM) developed along with a deep chlorophyll maximum during the summer and was located just below the mixed layer . At this depth, phytoplankton had favourable light and nutrient conditions to grow and produce oxygen, which was not subject to immediate outgassing. The oxygen concentration in the DOM was not constant, but decreased, then increased again until the end of the mission. Intrusions of oxygen rich water are also visible throughout the mission. These are probably due to mesoscale events through the horizontal transport of oxygen and/or nutrients that can enhance productivity, particularly at the edge of the fronts. We calculate net community production (NCP) by analysing the variation in oxygen with time. Two methods have been proposed. The classical oxygen budget method assumes that changes in oxygen are due to the sum of air-sea flux, isopycnal advection, diapycnal mixing and NCP. ERA

  9. Effect of Mechanical Alloying Atmospheres and Oxygen Concentration on Mechanical Properties of ODS Ferritic Steels

    International Nuclear Information System (INIS)

    Noh, Sanghoon; Choi, Byoungkwon; Han, Changhee; Kim, Kibaik; Kang, Sukhoon; Chun, Youngbum; Kim, Taekyu

    2013-01-01

    Finely dispersed nano-oxide particles with a high number density in the homogeneous grain matrix are essential to achieve superior mechanical properties at high temperatures, and these unique microstructures can be obtained through the mechanical alloying (MA) and hot consolidation process. The microstructure and mechanical property of ODS steel significantly depends on its powder property and the purity after the MA process. These contents should be carefully controlled to improve the mechanical property at elevated temperature. In particular, appropriate the control of oxygen concentration improves the mechanical property of ODS steel at high temperature. An effective method is to control the mechanical alloying atmosphere by high purity inert gas. In the present study, the effects of mechanical alloying atmospheres and oxygen concentration on the mechanical property of ODS steel were investigated. ODS ferritic alloys were fabricated in various atmospheres, and the HIP process was used to investigate the effects of MA atmospheres and oxygen concentration on the microstructure and mechanical property. ODS ferritic alloys milled in an Ar-H 2 mixture, and He is effective to reduce the excess oxygen concentration. The YH 2 addition made an extremely reduced oxygen concentration by the internal oxygen reduction reaction and resulted in a homogeneous microstructure and superior creep strength

  10. Effects of ambient oxygen concentration on biodiesel and diesel spray combustion under simulated engine conditions

    KAUST Repository

    Zhang, Ji

    2013-08-01

    This study investigates the effect of ambient oxygen concentration on biodiesel and diesel spray combustion under simulated compression-ignition engine conditions in a constant-volume chamber. The apparent heat release rate (AHRR) is calculated based on the measured pressure. High-speed imaging of OH* chemiluminescence and natural luminosity (NL) is employed to visualize the combustion process. Temporally and spatially resolved NL and OH* contour plots are obtained. The result indicates that AHRR depends monotonically on the ambient oxygen concentration for both fuels. A lower oxygen concentration yields a slower AHRR increase rate, a lower peak AHRR value, but a higher AHRR value during the burn-out stage when compared with higher ambient oxygen concentration conditions. OH* chemiluminescence and NL contours indicate that biodiesel may experience a longer premixed-combustion duration. The 18% ambient O2 condition works better for biodiesel than diesel in reducing soot luminosity. With 12% O2, diesel combustion is significantly degraded. However, both fuels experience low temperature combustion at 10% O2. These results may imply that biodiesel is able to achieve the desired lower soot production under a moderate oxygen level with higher combustion efficiency, while diesel needs to be burned under very low ambient oxygen concentration for low soot production. © 2013 Elsevier Ltd.

  11. Effects of ambient oxygen concentration on biodiesel and diesel spray combustion under simulated engine conditions

    KAUST Repository

    Zhang, Ji; Jing, Wei; Roberts, William L.; Fang, Tiegang

    2013-01-01

    This study investigates the effect of ambient oxygen concentration on biodiesel and diesel spray combustion under simulated compression-ignition engine conditions in a constant-volume chamber. The apparent heat release rate (AHRR) is calculated based on the measured pressure. High-speed imaging of OH* chemiluminescence and natural luminosity (NL) is employed to visualize the combustion process. Temporally and spatially resolved NL and OH* contour plots are obtained. The result indicates that AHRR depends monotonically on the ambient oxygen concentration for both fuels. A lower oxygen concentration yields a slower AHRR increase rate, a lower peak AHRR value, but a higher AHRR value during the burn-out stage when compared with higher ambient oxygen concentration conditions. OH* chemiluminescence and NL contours indicate that biodiesel may experience a longer premixed-combustion duration. The 18% ambient O2 condition works better for biodiesel than diesel in reducing soot luminosity. With 12% O2, diesel combustion is significantly degraded. However, both fuels experience low temperature combustion at 10% O2. These results may imply that biodiesel is able to achieve the desired lower soot production under a moderate oxygen level with higher combustion efficiency, while diesel needs to be burned under very low ambient oxygen concentration for low soot production. © 2013 Elsevier Ltd.

  12. Synthesis of low oxygen concentration molybdenum nitride films

    International Nuclear Information System (INIS)

    Roberson, S.L.; Davis, R.F.; Finello, D.

    1998-01-01

    Polycrystalline, small grain size, 15 μm thick Mo x N (x = 1 and 2) films containing ∼60 at.% γ-Mo 2 N and ∼40 at.% δ-MoN and void of Auger detectable concentrations of molybdenum oxides, have been prepared on 50-μm thick nitrided Ti substrates via programmed reaction and subsequent anneal at 750 C for 2 h of the precursor MoO 3 films with NH 3 . The latter films were prepared via liquid spray pyrolysis of an MoCl 5 /methanol mixture in air at 500 C. By contrast, residual MoO 2 occurred near the film-substrate interface in Mo x N films produced using the same programmed reaction but where MoO 3 had been deposited on bare Ti substrates. The change in density of MoO 3 (ρ = 4.69 gcm -3 ) to γ-Mo 2 N (ρ = 9.50 gcm -3 ) and δ-MoN (ρ = 9.05 gcm -3 ), as well as the nature of the topotactic conversion, produced grains which had a calculated average size of 10 nm and which exhibited good adhesion to the substrate. Variations in the conversion heating rates and the NH 3 flow rates also affected both the phase composition and the average grain size of the intermediate and the final reaction products. Scanning electron microscopy (SEM) of the Mo x N films revealed a highly porous surface morphology. (orig.)

  13. Water quality and processes affecting dissolved oxygen concentrations in the Blackwater River, Canaan Valley, West Virginia

    Science.gov (United States)

    Waldron, M.C.; Wiley, J.B.

    1996-01-01

    The water quality and environmental processes affecting dissolved oxygen were determined for the Blackwater River in Canaan Valley, West Virginia. Canaan Valley is oval-shaped (14 miles by 5 miles) and is located in the Allegheny Mountains at an average elevation of 3,200 feet above sea level. Tourism, population, and real estate development have increased in the past two decades. Most streams in Canaan Valley are a dilute calcium magnesium bicarbonate-type water. Streamwater typicaly was soft and low in alkalinity and dissolved solids. Maximum values for specific conductance, hardness, alkalinity, and dissolved solids occurred during low-flow periods when streamflow was at or near baseflow. Dissolved oxygen concentrations are most sensitive to processes affecting the rate of reaeration. The reaeration is affected by solubility (atmospheric pressure, water temperature, humidity, and cloud cover) and processes that determine stream turbulence (stream depth, width, velocity, and roughness). In the headwaters, photosynthetic dissolved oxygen production by benthic algae can result in supersaturated dissolved oxygen concentrations. In beaver pools, dissolved oxygen consumption from sediment oxygen demand and carbonaceous biochemical oxygen demand can result in dissolved oxygen deficits.

  14. Dissolved oxygen concentration in the medium during cell culture: Defects and improvements.

    Science.gov (United States)

    Zhang, Kuan; Zhao, Tong; Huang, Xin; He, Yunlin; Zhou, Yanzhao; Wu, Liying; Wu, Kuiwu; Fan, Ming; Zhu, Lingling

    2016-03-01

    In vitro cell culture has provided a useful model to study the effects of oxygen on cellular behavior. However, it remains unknown whether the in vitro operations themselves affect the medium oxygen levels and the living states of cells. In addition, a prevailing controversy is whether reactive oxygen species (ROS) production is induced by continuous hypoxia or reoxygenation. In this study, we have measured the effects of different types of cell culture containers and the oxygen environment where medium replacement takes place on the actual oxygen tension in the medium. We found that the deviations of oxygen concentrations in the medium are much greater in 25-cm(2) flasks than in 24-well plates and 35-mm dishes. The dissolved oxygen concentrations in the medium were increased after medium replacement in normoxia, but remained unchanged in glove boxes in which the oxygen tension remained at a low level (11.4, 5.7, and 0.5% O2 ). We also found that medium replacement in normoxia increased the number of ROS-positive cells and reduced the cell viability; meanwhile, medium replacement in a glove box did not produce the above effects. Therefore, we conclude that the use of 25-cm(2) flasks should be avoided and demonstrate that continuous hypoxia does not produce ROS, whereas the reoxygenation that occurs during the harvesting of cells leads to ROS and induces cell death. © 2015 International Federation for Cell Biology.

  15. Photochemical characterization of water samples from Minnesota and Vermont sites with malformed frogs: potential influence of photosensitization by singlet molecular oxygen (1O2) and free radicals on aquatic toxicity

    International Nuclear Information System (INIS)

    Bilski, P.; Burkhart, J.G.; Chignell, C.F.

    2003-01-01

    Environmental pollutants activated by UV sunlight may have contributed to the recent decline in frog populations and the concomitant increase in malformations in the USA and abroad. UV radiation is able to mutate DNA and to initiate photosensitization processes that generate mutagenic and biologically disruptive oxygen transients. We have examined water from selected sites in Minnesota and Vermont using singlet molecular oxygen ( 1 O 2 ), detected by its phosphorescence and free radicals detected by spin trapping, as markers for photosensitization. Water from a pond in Minnesota with malformed frogs, which also causes malformations in the laboratory, photosensitized more 1 O 2 , even though it absorbed less UV light compared to water from a site that did not cause malformations. This suggested that unknown natural or pollutant agents were present, and that photosensitization may be involved. Although UV irradiation of the two Minnesota water samples in the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) revealed the presence of the DMPO/·OH, DMPO/·H(e aq - ) and DMPO/·C(unknown) adducts there were no qualitative or quantitative differences between them. We also examined water samples from several sites in Vermont, and compared them by measuring the quantum yield of 1 O 2 photosensitization. While all the Vermont samples produced a small amount of 1 O 2 , there was no clear correlation with the incidence of frog malformations. However, the samples differed strongly in absorption spectra and the ability to quench 1 O 2 . These factors may determine how much UV light is absorbed and converted into chemical reactions. Our results show that photochemical characterization of 1 O 2 photosensitization is possible in untreated natural water samples. Photosensitization falls into the category of global factors that may be closely associated with the effects of UV irradiation of the Earth's environments. Thus, photosensitization might be an important

  16. Photochemical characterization of water samples from Minnesota and Vermont sites with malformed frogs: potential influence of photosensitization by singlet molecular oxygen ({sup 1}O{sub 2}) and free radicals on aquatic toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Bilski, P.; Burkhart, J.G.; Chignell, C.F

    2003-11-19

    Environmental pollutants activated by UV sunlight may have contributed to the recent decline in frog populations and the concomitant increase in malformations in the USA and abroad. UV radiation is able to mutate DNA and to initiate photosensitization processes that generate mutagenic and biologically disruptive oxygen transients. We have examined water from selected sites in Minnesota and Vermont using singlet molecular oxygen ({sup 1}O{sub 2}), detected by its phosphorescence and free radicals detected by spin trapping, as markers for photosensitization. Water from a pond in Minnesota with malformed frogs, which also causes malformations in the laboratory, photosensitized more {sup 1}O{sub 2}, even though it absorbed less UV light compared to water from a site that did not cause malformations. This suggested that unknown natural or pollutant agents were present, and that photosensitization may be involved. Although UV irradiation of the two Minnesota water samples in the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) revealed the presence of the DMPO/{center_dot}OH, DMPO/{center_dot}H(e{sub aq}{sup -}) and DMPO/{center_dot}C(unknown) adducts there were no qualitative or quantitative differences between them. We also examined water samples from several sites in Vermont, and compared them by measuring the quantum yield of {sup 1}O{sub 2} photosensitization. While all the Vermont samples produced a small amount of {sup 1}O{sub 2}, there was no clear correlation with the incidence of frog malformations. However, the samples differed strongly in absorption spectra and the ability to quench {sup 1}O{sub 2}. These factors may determine how much UV light is absorbed and converted into chemical reactions. Our results show that photochemical characterization of {sup 1}O{sub 2} photosensitization is possible in untreated natural water samples. Photosensitization falls into the category of global factors that may be closely associated with the effects of

  17. Singlets of fermionic gauge symmetries

    NARCIS (Netherlands)

    Bergshoeff, E.A.; Kallosh, R.E.; Rahmanov, M.A.

    1989-01-01

    We investigate under which conditions singlets of fermionic gauge symmetries which are "square roots of gravity" can exist. Their existence is non-trivial because there are no fields neutral in gravity. We tabulate several examples of singlets of global and local supersymmetry and κ-symmetry and

  18. Microfabricated Collector-Generator Electrode Sensor for Measuring Absolute pH and Oxygen Concentrations.

    Science.gov (United States)

    Dengler, Adam K; Wightman, R Mark; McCarty, Gregory S

    2015-10-20

    Fast-scan cyclic voltammetry (FSCV) has attracted attention for studying in vivo neurotransmission due to its subsecond temporal resolution, selectivity, and sensitivity. Traditional FSCV measurements use background subtraction to isolate changes in the local electrochemical environment, providing detailed information on fluctuations in the concentration of electroactive species. This background subtraction removes information about constant or slowly changing concentrations. However, determination of background concentrations is still important for understanding functioning brain tissue. For example, neural activity is known to consume oxygen and produce carbon dioxide which affects local levels of oxygen and pH. Here, we present a microfabricated microelectrode array which uses FSCV to detect the absolute levels of oxygen and pH in vitro. The sensor is a collector-generator electrode array with carbon microelectrodes spaced 5 μm apart. In this work, a periodic potential step is applied at the generator producing transient local changes in the electrochemical environment. The collector electrode continuously performs FSCV enabling these induced changes in concentration to be recorded with the sensitivity and selectivity of FSCV. A negative potential step applied at the generator produces a transient local pH shift at the collector. The generator-induced pH signal is detected using FSCV at the collector and correlated to absolute solution pH by postcalibration of the anodic peak position. In addition, in oxygenated solutions a negative potential step at the generator produces hydrogen peroxide by reducing oxygen. Hydrogen peroxide is detected with FSCV at the collector electrode, and the magnitude of the oxidative peak is proportional to absolute oxygen concentrations. Oxygen interference on the pH signal is minimal and can be accounted for with a postcalibration.

  19. Modeling the oxygen microheterogeneity of tumors for photodynamic therapy dosimetry

    Science.gov (United States)

    Pogue, Brian W.; Paulsen, Keith D.; O'Hara, Julia A.; Hoopes, P. Jack; Swartz, Harold

    2000-03-01

    Photodynamic theory of tumors uses optical excitation of a sensitizing drug within tissue to produce large deposits of singlet oxygen, which are thought to ultimately cause the tumor destruction. Predicting dose deposition of singlet oxygen in vivo is challenging because measurement of this species in vivo is not easily achieved. But it is possible to follow the concentration of oxygen in vivo, and so measuring the oxygen concentration transients during PDT may provide a viable method of estimating the delivered dose of singlet oxygen. However modeling the microscopic heterogeneity of the oxygen distribution within a tumor is non-trivial, and predicting the microscopic dose deposition requires further study, but this study present the framework and initial calibration needed or modeling oxygen transport in complex geometries. Computational modeling with finite elements provides a versatile structure within which oxygen diffusion and consumption can be modeled within realistic tissue geometries. This study develops the basic tools required to simulate a tumor region, and examines the role of (i) oxygen supply and consumption rates, (ii) inter- capillary spacing, (iii) photosensitizer distribution, and (iv) differences between simulated tumors and those derived directly from histology. The result of these calculations indicate that realistic tumor tissue capillary networks can be simulated using the finite element method, without excessive computational burden for 2D regions near 1 mm2, and 3D regions near 0.1mm3. These simulations can provide fundamental information about tissue and ways to implement appropriate oxygen measurements. These calculations suggest that photodynamic therapy produces the majority of singlet oxygen in and near the blood vessels, because these are the sites of highest oxygen tension. These calculations support the concept that tumor vascular regions are the major targets for PDT dose deposition.

  20. Sulfide-inhibition of mitochondrial respiration at very low oxygen concentrations.

    Science.gov (United States)

    Matallo, J; Vogt, J; McCook, O; Wachter, U; Tillmans, F; Groeger, M; Szabo, C; Georgieff, M; Radermacher, P; Calzia, E

    2014-09-15

    Our aim was to study the ability of an immortalized cell line (AMJ2-C11) to sustain aerobic cell respiration at decreasing oxygen concentrations under continuous sulfide exposure. We assumed that the rate of elimination of sulfide through the pathway linked to the mitochondrial respiratory chain and therefore operating under aerobic conditions, should decrease with limiting oxygen concentrations. Thus, sulfide's inhibition of cellular respiration would occur faster under continuous sulfide exposure when the oxygen concentration is in the very low range. The experiments were performed with an O2K-oxygraph (Oroboros Instruments) by suspending 0.5-1×10(6) cells in 2 ml of continuously stirred respiration medium at 37 °C and calculating the oxygen flux (JO2) as the negative derivative of the oxygen concentration in the medium. The cells were studied in two different metabolic states, namely under normal physiologic respiration (1) and after uncoupling of mitochondrial respiration (2). Oxygen concentration was controlled by means of a titration-injection pump, resulting in average concentration values of 0.73±0.05 μM, 3.1±0.2 μM, and 6.2±0.2 μM. Simultaneously we injected a 2 mM Na2S solution at a continuous rate of 10 μl/s in order to quantify the titration-time required to reduce the JO2 to 50% of the initial respiratory activity. Under the lowest oxygen concentration this effect was achieved after 3.5 [0.3;3.5] and 11.7 [6.2;21.2]min in the uncoupled and coupled state, respectively. This time was statistically significantly shorter when compared to the intermediate and the highest O2 concentrations tested, which yielded values of 24.6 [15.5;28.1]min (coupled) and 35.9 [27.4;59.2]min (uncoupled), as well as 42.4 [27.5;42.4]min (coupled) and 51.5 [46.4;51.7]min (uncoupled). All data are medians [25%, and 75% percentiles]. Our results confirm that the onset of inhibition of cell respiration by sulfide occurs earlier under a continuous exposure when approaching

  1. Oxygenation level and hemoglobin concentration in experimental tumor estimated by diffuse optical spectroscopy

    Science.gov (United States)

    Orlova, A. G.; Kirillin, M. Yu.; Volovetsky, A. B.; Shilyagina, N. Yu.; Sergeeva, E. A.; Golubiatnikov, G. Yu.; Turchin, I. V.

    2017-07-01

    Using diffuse optical spectroscopy the level of oxygenation and hemoglobin concentration in experimental tumor in comparison with normal muscle tissue of mice have been studied. Subcutaneously growing SKBR-3 was used as a tumor model. Continuous wave fiber probe diffuse optical spectroscopy system was employed. Optical properties extraction approach was based on diffusion approximation. Decreased blood oxygen saturation level and increased total hemoglobin content were demonstrated in the neoplasm. The main reason of such differences between tumor and norm was significant elevation of deoxyhemoglobin concentration in SKBR-3. The method can be useful for diagnosis of tumors as well as for study of blood flow parameters of tumor models with different angiogenic properties.

  2. Gaugino mass without singlets

    International Nuclear Information System (INIS)

    Giudice, Gian F.; Luty, Markus A.; Murayama, Hitoshi; Rattazzi, Riccardo

    1998-01-01

    In models with dynamical supersymmetry breaking in the hidden sector, the gaugino masses in the observable sector have been believed to be extremely suppressed (below 1 keV), unless there is a gauge singlet in the hidden sector with specific couplings to the observable sector gauge multiplets. We point out that there is a pure supergravity contribution to gaugino masses at the quantum level arising from the superconformal anomaly. Our results are valid to all orders in perturbation theory and are related to the ''exact'' beta functions for soft terms. There is also an anomaly contribution to the A terms proportional to the beta function of the corresponding Yukawa coupling. The gaugino masses are proportional to the corresponding gauge beta functions, and so do not satisfy the usual GUT relations

  3. Fluorescence measurement of atomic oxygen concentration in a dielectric barrier discharge

    Science.gov (United States)

    Dvořák, P.; Mrkvičková, M.; Obrusník, A.; Kratzer, J.; Dědina, J.; Procházka, V.

    2017-06-01

    Concentration of atomic oxygen was measured in a volume dielectric barrier discharge (DBD) ignited in mixtures of Ar + O2(+ H2) at atmospheric pressure. Two-photon absorption laser induced fluorescence (TALIF) of atomic oxygen was used and this method was calibrated by TALIF of Xe in a mixture of argon and a trace of xenon. The calibration was performed at atmospheric pressure and it was shown that quenching by three-body collisions has negligible effect on the life time of excited Xe atoms. The concentration of atomic oxygen in the DBD was around 1021 m-3 and it was stable during the whole discharge period. The concentration did not depend much on the electric power delivered to the discharge provided that the power was sufficiently high so that the visible discharge filled the whole reactor volume. Both the addition of hydrogen or replacing of argon by helium led to a significant decrease of atomic oxygen concentration. The TALIF measurements of O concentration levels in the DBD plasma performed in this work are made use of e.g. in the field analytical chemistry. The results contribute to understanding the processes of analyte hydride preconcentration and subsequent atomization in the field of trace element analysis where DBD plasma atomizers are employed.

  4. Influence of dissolved oxygen concentration on the toxicity of potassium cyanide to rainbow trout. [Salmo gairdneri

    Energy Technology Data Exchange (ETDEWEB)

    Downing, K M

    1954-01-01

    The present work was undertaken to see if similar results were obtained when fish were tested in a continuous flow of water in which the concentrations of oxygen and cyanide were kept constant. Periods of survival were measured this way to minimize distortion of results by accumulation of metabolic waste, depletion of oxygen or depletion of poison. Results are summarized as follows: rainbow trout survival in potassium cyanide increased with increase in dissolved oxygen; increase in survival times did not decline as oxygen saturation was approached; and medium survival times of 3.3 minutes or less were normally distributed while those of greater than 13 minutes were log normally distributed. 6 references, 1 figure.

  5. Singlet-triplet annihilation in single LHCII complexes

    NARCIS (Netherlands)

    Gruber, J.M.; Chmeliov, J.; Kruger, T.P.J.; Valkunas, L.; van Grondelle, R.

    2015-01-01

    In light harvesting complex II (LHCII) of higher plants and green algae, carotenoids (Cars) have an important function to quench chlorophyll (Chl) triplet states and therefore avoid the production of harmful singlet oxygen. The resulting Car triplet states lead to a non-linear self-quenching

  6. Search for Singlet Fission Chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Havlas, Z.; Akdag, A.; Smith, M. B.; Dron, P.; Johnson, J. C.; Nozik, A. J.; Michl, J.

    2012-01-01

    Singlet fission, in which a singlet excited chromophore shares its energy with a ground-state neighbor and both end up in their triplet states, is of potential interest for solar cells. Only a handful of compounds, mostly alternant hydrocarbons, are known to perform efficiently. In view of the large number of conditions that a successful candidate for a practical cell has to meet, it appears desirable to extend the present list of high performers to additional classes of compounds. We have (i) identified design rules for new singlet fission chromophores and for their coupling to covalent dimers, (ii) synthesized them, and (iii) evaluated their performance as neat solids or covalent dimers.

  7. Reduction of oxygen concentration by heater design during Czochralski Si growth

    Science.gov (United States)

    Zhou, Bing; Chen, Wenliang; Li, Zhihui; Yue, Ruicun; Liu, Guowei; Huang, Xinming

    2018-02-01

    Oxygen is one of the highest-concentration impurities in single crystals grown by the Czochralski (CZ) process, and seriously impairs the quality of the Si wafer. In this study, computer simulations were applied to design a new CZ system. A more appropriate thermal field was acquired by optimization of the heater structure. The simulation results showed that, compared with the conventional system, the oxygen concentration in the newly designed CZ system was reduced significantly throughout the entire CZ process because of the lower crucible wall temperature and optimized convection. To verify the simulation results, experiments were conducted on an industrial single-crystal furnace. The experimental results showed that the oxygen concentration was reduced significantly, especially at the top of the CZ-Si ingot. Specifically, the oxygen concentration was 6.19 × 1017 atom/cm3 at the top of the CZ-Si ingot with the newly designed CZ system, compared with 9.22 × 1017 atom/cm3 with the conventional system. Corresponding light-induced degradation of solar cells based on the top of crystals from the newly designed CZ system was 1.62%, a reduction of 0.64% compared with crystals from the conventional system (2.26%).

  8. Dependence of Initial Oxygen Concentration on Ozone Yield Using Inductive Energy Storage System Pulsed Power Generator

    Science.gov (United States)

    Go, Tomio; Tanaka, Yasushi; Yamazaki, Nobuyuki; Mukaigawa, Seiji; Takaki, Koichi; Fujiwara, Tamiya

    Dependence of initial oxygen concentration on ozone yield using streamer discharge reactor driven by an inductive energy storage system pulsed power generator is described in this paper. Fast recovery type diodes were employed as semiconductor opening switch to interrupt a circuit current within 100 ns. This rapid current change produced high-voltage short pulse between a secondary energy storage inductor. The repetitive high-voltage short pulse was applied to a 1 mm diameter center wire electrode placed in a cylindrical pulse corona reactor. The streamer discharge successfully occurred between the center wire electrode and an outer cylinder ground electrode of 2 cm inner diameter. The ozone was produced with the streamer discharge and increased with increasing pulse repetition rate. The ozone yield changed in proportion to initial oxygen concentration contained in the injected gas mixture at 800 ns forward pumping time of the current. However, the decrease of the ozone yield by decreasing oxygen concentration in the gas mixture at 180 ns forward pumping time of the current was lower than the decrease at 800 ns forward pumping time of the current. This dependence of the initial oxygen concentration on ozone yield at 180 ns forward pumping time is similar to that of dielectric barrier discharge reactor.

  9. The Relationship between Mollusks and Oxygen Concentrations in Todos Santos Bay, Baja California, Mexico

    Directory of Open Access Journals (Sweden)

    J. Gabriel Kuk-Dzul

    2016-01-01

    Full Text Available This study describes the relationship between mollusks, physicochemical properties of seawater, and sediments under natural conditions of low impact. Thirty-nine stations were sampled in October 1994 using a Van Veen grab (0.1 m−2. Temperature, salinity, and dissolved oxygen (DO concentrations of bottom water were obtained with a CTD. Organic matter content and sediment grain analysis were determined. A total of 836 mollusks were collected. Gastropoda was the most abundant (52% and diverse class with 27 genera, followed by Bivalvia with eight genera and Scaphopoda with only one genus. According to CCA analysis, dominant mollusks were significantly related with high DO concentrations. Donax, Natica, Acteocina, Bulla, Anachis, Odostomia, and Crucibulum can be classified as sensitive genera because they were found mainly in high oxygen concentrations (3.1–5.6 mL L−1; on the other hand, Cardiomya, Nuculana, Laevicardium, Chione, Truncatella, and Dentalium can be classified as tolerant genera (1.0–5.6 mL L−1. Todos Santos Bay hosts a diverse malacological fauna (36 genera; our results show that the dominant genera were mainly related to high dissolved oxygen concentrations. Mollusks can be a useful tool in environmental monitoring programs related with oxygen depletion in coastal areas.

  10. Investigation on the improved radiation hardness of silicon detectors with high oxygen concentration

    CERN Document Server

    Moll, Michael; Lindström, G

    2000-01-01

    We present an investigation on the influence of the oxygen concentration on radiation-induced changes in the effective doping concentration of silicon detectors. Diodes fabricated from silicon with interstitial oxygen content ranging from below 2*10/sup 14/ to 9*10/sup 17/ cm/sup -3/ have been irradiated with fast neutrons up to a fluence of 2*10/sup 15/ cm/sup -2/. Our main interest focused on the so-called stable damage component in the change of the effective doping concentration being of prime importance for the application of silicon detectors in high-energy physics experiments. We demonstrate, that with a high oxygen enrichment the donor removal is appreciably reduced, reaching a value of only 10601130f the initial doping concentration for [O/sub i/]=9*10/sup 17/ cm/sup -3/, while for normal detector grade material with [O/sub i/] below 5*10/sup 16/ cm /sup -3/ that value is 60-90Furthermore, we show that the fluence proportional introduction of stable acceptors is independent of the oxygen concentratio...

  11. Innovative encapsulated oxygen-releasing beads for bioremediation of BTEX at high concentration in groundwater.

    Science.gov (United States)

    Lin, Chi-Wen; Wu, Chih-Hung; Guo, Pei-Yu; Chang, Shih-Hsien

    2017-12-15

    Both a low concentration of dissolved oxygen and the toxicity of a high concentration of BTEX inhibit the bioremediation of BTEX in groundwater. A novel method of preparing encapsulated oxygen-releasing beads (encap-ORBs) for the biodegradation of BTEX in groundwater was developed. Experimental results show that the integrality and oxygen-releasing capacity of encap-ORBs exceeded those of ORBs. The use of polyvinyl alcohol (PVA) with high M.W. to prepare encap-ORBs improved their integrality. The encap-ORBs effectively released oxygen for 128 days. High concentration of BTEX (480 mg L -1 ) inhibited the biodegradation by the free cells. Immobilization of degraders in the encap-ORB alleviated the inhibition. Scanning electron microscope analysis reveals that the BTEX degraders grew on the surface of encap-ORB after bioremediation. The above results indicate that the encap-ORBs were effective in the bioremediation of BTEX at high concentration in groundwater. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Startup and oxygen concentration effects in a continuous granular mixed flow autotrophic nitrogen removal reactor.

    Science.gov (United States)

    Varas, Rodrigo; Guzmán-Fierro, Víctor; Giustinianovich, Elisa; Behar, Jack; Fernández, Katherina; Roeckel, Marlene

    2015-08-01

    The startup and performance of the completely autotrophic nitrogen removal over nitrite (CANON) process was tested in a continuously fed granular bubble column reactor (BCR) with two different aeration strategies: controlling the oxygen volumetric flow and oxygen concentration. During the startup with the control of oxygen volumetric flow, the air volume was adjusted to 60mL/h and the CANON reactor had volumetric N loadings ranging from 7.35 to 100.90mgN/Ld with 36-71% total nitrogen removal and high instability. In the second stage, the reactor was operated at oxygen concentrations of 0.6, 0.4 and 0.2mg/L. The best condition was 0.2 mgO2/L with a total nitrogen removal of 75.36% with a CANON reactor activity of 0.1149gN/gVVSd and high stability. The feasibility and effectiveness of CANON processes with oxygen control was demonstrated, showing an alternative design tool for efficiently removing nitrogen species. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Oxygen diffusion-concentration in phospholipidic model membranes. An ESR-saturation study

    International Nuclear Information System (INIS)

    Vachon, A.; Lecomte, C.; Berleur, F.

    1986-04-01

    Fully hydrated liposomes of dipalmitoyl-phosphatidylcholine were labelled with 5 (or 7, 10, 12, 16)-doxyl stearic acid at pH 6 and 8, and studied by the continuous wave ESR-saturation technique. The ESR spectral magnitude depends on the hyperfrequency power P and on both T 1 and T 2 relaxation times. Saturation, i.e. the non linearity of the spectral magnitude plotted versus √P can be quantified by a P1/2 parameter (power at which the signal is half as great as it would be without saturation). If we assume T 2 weakly modified by spin exchange between paramagnetic spin probe and oxygen in triplet state, P1/2 is inversely proportional to T 1 , and becomes a sensitive parameter to appreciate the oxygen transport (oxygen diffusion-concentration product) inside the bilayers. According to the DPPC bilayer phase transition diagrams, P1/2 (oxygen diffusion-concentration) is related to the thermodynamic state of the membrane. This technique provides further informations on a particular property of a radioprotective agent, cysteamine, which seems to inhibit spin-triplet exchange and hence maximizes T 1 (minimizes P1/2). Since radioprotective agents are known to act by scavenging radiation-induced free radicals and by inhibiting oxygen-dependent free radical processes, such a result may contribute to elucidate radioprotecting mechanisms

  14. The effects of oxygen level and glucose concentration on the metabolism of porcine TMJ disc cells.

    Science.gov (United States)

    Cisewski, S E; Zhang, L; Kuo, J; Wright, G J; Wu, Y; Kern, M J; Yao, H

    2015-10-01

    To determine the combined effect of oxygen level and glucose concentration on cell viability, ATP production, and matrix synthesis of temporomandibular joint (TMJ) disc cells. TMJ disc cells were isolated from pigs aged 6-8 months and cultured in a monolayer. Cell cultures were preconditioned for 48 h with 0, 1.5, 5, or 25 mM glucose DMEM under 1%, 5%, 10%, or 21% O2 level, respectively. The cell viability was measured using the WST-1 assay. ATP production was determined using the Luciferin-Luciferase assay. Collagen and proteoglycan synthesis were determined by measuring the incorporation of [2, 3-(3)H] proline and [(35)S] sulfate into the cells, respectively. TMJ disc cell viability significantly decreased (P oxygen levels significantly increased viability (P oxygen levels significantly reduced ATP production (P oxygen was significant in regards to cell viability (P oxygen are important, glucose is the limiting nutrient for TMJ disc cell survival. At low oxygen levels, the production of ATP, collagen, and proteoglycan are severely inhibited. These results suggest that steeper nutrient gradients may exist in the TMJ disc and it may be vulnerable to pathological events that impede nutrient supply. Copyright © 2015 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

  15. Radiation survival of cells from spheroids grown in different oxygen concentrations

    International Nuclear Information System (INIS)

    Franko, A.J.; Sutherland, R.M.

    1979-01-01

    The position of the internal, chronically hypoxic cells in spheroids was varied by alterations in the oxygen concentration in the growth medium. Such alterations were expected to cause large changes in the size of the radiobiologically hypoxic fraction. This was tested by growing and irradiating spheroids in oxygen concentrations between 5 and 20.3%, ensuring that the irradiation and growth conditions were as similar as possible. The survival curves appeared to be linear below a surviving fraction of 3 x 10 -2 , and the slopes were intermediate between the slopes of control curves for cells from spheroids irradiated in nitrogen or when fully oxygenated. Thus direct estimates of the hypoxic fractions could not be made. Two models of oxygen diffusion might explain the data. One model assumes that a large fraction of cells was fully hypoxic (radiobiologically) and that these internal, G 1 -confined, chronically hypoxic cells had a lower inherent radioresistance than the outer proliferating cells. Evidence was presented which indicated that this model was unlikely to be correct. The other model assumes that the inherent radioresistance was equal throughout the spheroid, and that the innermost cells died before the oxygen concentration was reduced sufficiently to cause full hypoxic protection. Theoretical survival curves based on this model were generated using the measured geometries ofthe spheroids and multitarget single-hit survival theory. Acceptable agreement with the postulate that the innermost cells of spheroids die at between 0.2 and 0.4% oxygen was obtained. These data may have implications regarding the relative contributions of chronic and acute hypoxia to the fraction of hypoxic cells in tumors

  16. Influence of the dissolved oxygen concentration on the penicillin biosynthetic pathway in steady-state cultures of Penicillium chrysogenum

    DEFF Research Database (Denmark)

    Henriksen, Claus Maxel; Nielsen, Jens Bredal; Villadsen, John

    1997-01-01

    The influence the of dissolved oxygen concentration on penicillin biosynthesis was studied in steady-state continuous cultures of a high-yielding strain of Penicillium chrysogenum operated at a dilution rate of 0.05 h-l. The dissolved oxygen concentration was varied between 0.019 and 0.344 m...... penicillin productivity decreases, and a value of 17 (mu mol/g of DW)/h was obtained when the dissolved oxygen concentration was 0.042 mM. A further lowering of the dissolved oxygen concentration to 0.019 mM resulted in the loss of penicillin production. However, penicillin productivity was instantly...

  17. Detection of Molecular Oxygen at Low Concentrations Using Quartz Enhanced Photoacoustic Spectroscopy

    Directory of Open Access Journals (Sweden)

    Andreas Pohlkötter

    2010-09-01

    Full Text Available Molecular oxygen is detected at low concentrations using photoacoustic spectroscopy despite its unfavorable photoacoustic properties. The system consists of a seed laser diode, a tapered amplifier and a quartz tuning fork based spectrophone, thus employing quartz enhanced photoacoustic spectroscopy (QEPAS. With this system a detection limit of 13 ppm is reached with a compact and long term stable setup. Further improvement of the detection limit is possible by adding suitable gases to the sample gas that promote the radiationless de-excitation of the oxygen molecules.

  18. Short-term molecular acclimation processes of legume nodules to increased external oxygen concentration

    Directory of Open Access Journals (Sweden)

    Ulrike eAvenhaus

    2016-01-01

    Full Text Available Nitrogenase is an oxygen labile enzyme. Microaerobic conditions within the infected zone of nodules are maintained primarily by an oxygen diffusion barrier located in the nodule cortex. Flexibility of the oxygen diffusion barrier is important for the acclimation processes of nodules in response to changes in external oxygen concentration. The hypothesis of the present study was that there are additional molecular mechanisms involved. Nodule activity of Medicago truncatula plants were continuously monitored during a change from 21 to 25 or 30 % oxygen around root nodules by measuring nodule H2 evolution. Within about two minutes of the increase in oxygen concentration, a steep decline in nitrogenase activity occurred. A quick recovery commenced about eight minutes later. A qPCR-based analysis of the expression of genes for nitrogenase components showed a tendency towards upregulation during the recovery. The recovery resulted in a new constant activity after about 30 minutes, corresponding to approximately 90 % of the pre-treatment level. An RNAseq-based comparative transcriptome profiling of nodules at that point in time revealed that genes for nodule-specific cysteine-rich (NCR peptides, defensins, leghaemoglobin and chalcone and stilbene synthase were significantly upregulated when considered as a gene family. A gene for a nicotianamine synthase-like protein (Medtr1g084050 showed a strong increase in count number. The gene appears to be of importance for nodule functioning, as evidenced by its consistently high expression in nodules and a strong reaction to various environmental cues that influence nodule activity. A Tnt1-mutant that carries an insert in the coding sequence (cds of that gene showed reduced nitrogen fixation and less efficient acclimation to an increased external oxygen concentration. It was concluded that sudden increases in oxygen concentration around nodules destroy nitrogenase, which is quickly counteracted by an increased

  19. Effect of reduced light and low oxygen concentration on germination, growth and establishment of some plants

    DEFF Research Database (Denmark)

    Yasin, Muhammad

    Many abiotic factors effect plants germination, growth, and development. This Ph.D. study elucidates the effect of reduced light, low oxygen and seed dormancy on germination and growth of some weed species, field crops and vegetables. One study describes the growth and developmental responses...... of some common, invasive and rare weed species to reduced light levels in greenhouse experiments. The seed germination response of some weed species, field crops, and vegetables to different oxygen concentrations was also quantified in the laboratory experiments. The effect of east-west (EW) and north...

  20. Investigation on the improved radiation hardness of silicon detectors with high oxygen concentration

    International Nuclear Information System (INIS)

    Moll, M.; Fretwurst, E.; Lindstroem, G.

    2000-01-01

    We present an investigation on the influence of the oxygen concentration on radiation-induced changes in the effective doping concentration of silicon detectors. Diodes fabricated from silicon with interstitial oxygen content ranging from below 2x10 14 to 9x10 17 cm -3 have been irradiated with fast neutrons up to a fluence of 2x10 15 cm -2 . Our main interest focused on the so-called stable damage component in the change of the effective doping concentration being of prime importance for the application of silicon detectors in high-energy physics experiments. We demonstrate, that with a high oxygen enrichment the donor removal is appreciably reduced, reaching a value of only 10% of the initial doping concentration for [O i ]=9x10 17 cm -3 , while for normal detector grade material with [O i ] below 5x10 16 cm -3 that value is 60-90%. Furthermore, we show that the fluence proportional introduction of stable acceptors is independent of the oxygen concentration with an averaged introduction rate of (1.49±0.03)x10 -2 cm -1 . Only one material was found exhibiting a significantly smaller value of about 0.6x10 -2 cm -1 and thus indicating the possibility to suppress the radiation-induced acceptor creation by material modification. Finally, we show that the experimental findings disagree in several important aspects with predictions made by microscopic defect kinetics models, leaving the physical background of some of the measured data as an open question

  1. Preservation of high glycolytic phenotype by establishing new acute lymphoblastic leukemia cell lines at physiologic oxygen concentration

    Energy Technology Data Exchange (ETDEWEB)

    Sheard, Michael A., E-mail: msheard@chla.usc.edu [Developmental Therapeutics Program, USC-CHLA Institute for Pediatric Clinical Research, Division of Hematology-Oncology, Children' s Hospital Los Angeles, 4650 Sunset Blvd., Los Angeles, CA 90027 (United States); Ghent, Matthew V., E-mail: mattghent@gmail.com [Department of Pathology, Keck School of Medicine, University of Southern California, Health Sciences Campus, Los Angeles, CA 90089 (United States); Cabral, Daniel J., E-mail: dcabral14@gmail.com [Cancer Center and Departments of Cell Biology & Biochemistry, Pharmacology & Neuroscience, Internal Medicine and Pediatrics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430 (United States); Lee, Joanne C., E-mail: joannebarnhart@gmail.com [Cancer Center and Departments of Cell Biology & Biochemistry, Pharmacology & Neuroscience, Internal Medicine and Pediatrics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430 (United States); Khankaldyyan, Vazgen, E-mail: khangaldian@yahoo.com [Developmental Therapeutics Program, USC-CHLA Institute for Pediatric Clinical Research, Division of Hematology-Oncology, Children' s Hospital Los Angeles, 4650 Sunset Blvd., Los Angeles, CA 90027 (United States); Ji, Lingyun, E-mail: lingyun.ji@med.usc.edu [Developmental Therapeutics Program, USC-CHLA Institute for Pediatric Clinical Research, Division of Hematology-Oncology, Children' s Hospital Los Angeles, 4650 Sunset Blvd., Los Angeles, CA 90027 (United States); Wu, Samuel Q., E-mail: swu@chla.usc.edu [Medical Genetics, Children' s Hospital Los Angeles, 4650 Sunset Blvd., Los Angeles, CA 90027 (United States); Kang, Min H., E-mail: min.kang@ttuhsc.edu [Cancer Center and Departments of Cell Biology & Biochemistry, Pharmacology & Neuroscience, Internal Medicine and Pediatrics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430 (United States); and others

    2015-05-15

    Cancer cells typically exhibit increased glycolysis and decreased mitochondrial oxidative phosphorylation, and they continue to exhibit some elevation in glycolysis even under aerobic conditions. However, it is unclear whether cancer cell lines employ a high level of glycolysis comparable to that of the original cancers from which they were derived, even if their culture conditions are changed to physiologically relevant oxygen concentrations. From three childhood acute lymphoblastic leukemia (ALL) patients we established three new pairs of cell lines in both atmospheric (20%) and physiologic (bone marrow level, 5%) oxygen concentrations. Cell lines established in 20% oxygen exhibited lower proliferation, survival, expression of glycolysis genes, glucose consumption, and lactate production. Interestingly, the effects of oxygen concentration used during cell line initiation were only partially reversible when established cell cultures were switched from one oxygen concentration to another for eight weeks. These observations indicate that ALL cell lines established at atmospheric oxygen concentration can exhibit relatively low levels of glycolysis and these levels are semi-permanent, suggesting that physiologic oxygen concentrations may be needed from the time of cell line initiation to preserve the high level of glycolysis commonly exhibited by leukemias in vivo. - Highlights: • Establishing new ALL cell lines in 5% oxygen resulted in higher glycolytic expression and function. • Establishing new ALL cell lines in 5% oxygen resulted in higher proliferation and lower cell death. • The divergent metabolic phenotypes selected in 5% and 20% oxygen are semi-permanent.

  2. Preservation of high glycolytic phenotype by establishing new acute lymphoblastic leukemia cell lines at physiologic oxygen concentration

    International Nuclear Information System (INIS)

    Sheard, Michael A.; Ghent, Matthew V.; Cabral, Daniel J.; Lee, Joanne C.; Khankaldyyan, Vazgen; Ji, Lingyun; Wu, Samuel Q.; Kang, Min H.

    2015-01-01

    Cancer cells typically exhibit increased glycolysis and decreased mitochondrial oxidative phosphorylation, and they continue to exhibit some elevation in glycolysis even under aerobic conditions. However, it is unclear whether cancer cell lines employ a high level of glycolysis comparable to that of the original cancers from which they were derived, even if their culture conditions are changed to physiologically relevant oxygen concentrations. From three childhood acute lymphoblastic leukemia (ALL) patients we established three new pairs of cell lines in both atmospheric (20%) and physiologic (bone marrow level, 5%) oxygen concentrations. Cell lines established in 20% oxygen exhibited lower proliferation, survival, expression of glycolysis genes, glucose consumption, and lactate production. Interestingly, the effects of oxygen concentration used during cell line initiation were only partially reversible when established cell cultures were switched from one oxygen concentration to another for eight weeks. These observations indicate that ALL cell lines established at atmospheric oxygen concentration can exhibit relatively low levels of glycolysis and these levels are semi-permanent, suggesting that physiologic oxygen concentrations may be needed from the time of cell line initiation to preserve the high level of glycolysis commonly exhibited by leukemias in vivo. - Highlights: • Establishing new ALL cell lines in 5% oxygen resulted in higher glycolytic expression and function. • Establishing new ALL cell lines in 5% oxygen resulted in higher proliferation and lower cell death. • The divergent metabolic phenotypes selected in 5% and 20% oxygen are semi-permanent

  3. Physiological oxygen concentration alters glioma cell malignancy and responsiveness to photodynamic therapy in vitro.

    Science.gov (United States)

    Albert, Ina; Hefti, Martin; Luginbuehl, Vera

    2014-11-01

    The partial pressure of oxygen (pO2) in brain tumors ranges from 5 to 15%. Nevertheless, the majority of in vitro experiments with glioblastoma multiforme (GBM) cell lines are carried out under an atmospheric pO2 of 19 to 21%. Recently, 5-aminolevulinic acid (5-ALA), a precursor of protoporphyrin IX (PpIX), has been introduced to neurosurgery to allow for photodynamic diagnosis and photodynamic therapy (PDT) in high-grade gliomas. Here, we investigate whether low pO2 affects GBM cell physiology, PpIX accumulation, or PDT efficacy. GBM cell lines (U-87 MG and U-251 MG) were cultured under atmospheric (pO2  =  19%) and physiological (pO2  =  9%) oxygen concentrations. PpIX accumulation and localization were investigated, and cell survival and cell death were observed following in vitro PDT. A physiological pO2 of 9% stimulated GBM cell migration, increased hypoxia-inducible factor (HIF)-1 alpha levels, and elevated resistance to camptothecin in U-87 MG cells compared to cultivation at a pO2 of 19%. This oxygen reduction did not alter 5-ALA-induced intracellular PpIX accumulation. However, physiological pO2 changed the responsiveness of U-87 MG but not of U-251 MG cells to in vitro PDT. Around 20% more irradiation light was required to kill U-87 MG cells at physiological pO2, resulting in reduced lactate dehydrogenase (LDH) release (one- to two-fold) and inhibition of caspase 3 activation. Reduction of oxygen concentration from atmospheric to a more physiological level can influence the malignant behavior and survival of GBM cell lines after in vitro PDT. Therefore, precise oxygen concentration control should be considered when designing and performing experiments with GBM cells.

  4. Impacts of nitric oxide and superoxide on renal medullary oxygen transport and urine concentration

    Science.gov (United States)

    Edwards, Aurélie; Layton, Anita T.

    2015-01-01

    The goal of this study was to investigate the reciprocal interactions among oxygen (O2), nitric oxide (NO), and superoxide (O2−) and their effects on medullary oxygenation and urinary output. To accomplish that goal, we developed a detailed mathematical model of solute transport in the renal medulla of the rat kidney. The model represents the radial organization of the renal tubules and vessels, which centers around the vascular bundles in the outer medulla and around clusters of collecting ducts in the inner medulla. Model simulations yield significant radial gradients in interstitial fluid oxygen tension (Po2) and NO and O2− concentration in the OM and upper IM. In the deep inner medulla, interstitial fluid concentrations become much more homogeneous, as the radial organization of tubules and vessels is not distinguishable. The model further predicts that due to the nonlinear interactions among O2, NO, and O2−, the effects of NO and O2− on sodium transport, osmolality, and medullary oxygenation cannot be gleaned by considering each solute's effect in isolation. An additional simulation suggests that a sufficiently large reduction in tubular transport efficiency may be the key contributing factor, more so than oxidative stress alone, to hypertension-induced medullary hypoxia. Moreover, model predictions suggest that urine Po2 could serve as a biomarker for medullary hypoxia and a predictor of the risk for hospital-acquired acute kidney injury. PMID:25651567

  5. Evaluation of dissolved oxygen and organic substances concentrations in water of the nature reserve Alluvium Zitavy

    International Nuclear Information System (INIS)

    Palaticka, A.; Noskovic, J.; Babosova, M.

    2007-01-01

    In 2006 concentrations of dissolved oxygen and organic substances were evaluated in water in the Nature Reserve Alluvium Zitavy (indirect method based on their oxidation by K 2 Cr 2 0 7 was used). The results are represented in mg of O 2 · dm -3 . Taking of samples took place in 6 sampling sites in regular month intervals. Based on obtained data and according to the standard STN 75 7221 (Water quality -The classification of the water surface quality) water in individual sampling sites was ranked into the classes of the .water surface quality. From the data it is clear that the concentrations of dissolved oxygen and organic substances in the Nature Reserve Alluvium Zitavy changed in dependence on sampling sites and time. The highest mean concentrations of dissolved oxygen in dependence on sampling time were found out in spring months and the lowest concentrations in summer months. They ranged from 1.6 mg 0 2 · dm -3 (July) to 9.0 mg O 2 · dm -3 (March). Falling dissolved oxygen values can be related to successive increase of water temperature, thus good conditions were created for decomposition of organic matter by microorganisms in water and sediments in which they use dissolved oxygen. In dependence on sampling place the highest mean concentration of dissolved oxygen was in sampling site No. 4 (6.0 mg 0 2 · dm -3 ) which is situated in the narrowest place in the NR. The lowest value was in sampling site No. 2 (3.6 mg 0 2 · dm -3 ) which is a typical wetland ecosystem. High mean values of COD Cr in dependence on sampling time were determined in summer months and low values during winter moths. Dependence of COD Cr values on sampling site was also manifested. The lowest mean value was obtained in sampling site No. 4 (59.5 mg · dm -3 ) and the highest value in sampling site No. 5 (97.1 mg · dm -3 ) which is also a typical wetland. Based on the results and according to the STN 75 7221 we ranked water in all sampling sites into the 5 th class of the water

  6. Impact of oxygen concentration on yields of DNA damages caused by ionizing radiation

    Czech Academy of Sciences Publication Activity Database

    Štěpán, Václav; Davídková, Marie

    2008-01-01

    Roč. 101, 012015 (2008), s. 1-4 ISSN 1742-6588. [Radiation Damage in Biomolecular Systems, RADAM'07. Dublin, 19.06.2007-22.06.2007] R&D Projects: GA ČR(CZ) GD202/05/H031; GA ČR GA202/05/2728 Institutional research plan: CEZ:AV0Z10480505 Keywords : radiation damage to DNA * oxygen concentration * theoretical modeling Subject RIV: BO - Biophysics

  7. Water relations link carbon and oxygen isotope discrimination to phloem sap sugar concentration in eucalyptus globulus

    International Nuclear Information System (INIS)

    Cernusak, L.A.; Farquhar, G.D.; Arthur, D.J; Pate, J.S.

    2002-01-01

    Full text: The carbon isotope ratio of phloem sap sugars has been previously observed to correlate strongly with the phloem sap sugar concentration in Eucalyptus globulus. We hypothesized that the correspondence between these two parameters results from co-linearity in their responses to variation in plant water potential. Carbon isotope discrimination is expected to decrease with decreasing plant water potential due to the influence of stomatal conductance on the ratio of intercellular to ambient CO 2 , concentrations (c 1 /c a ). Conversely, we expected the phloem sap sugar concentration to increase with decreasing plant water potential, thereby maintaining positive turgor pressure within the sieve tubes. The study comprised 40 individual Eucalyptus globulus trees growing in three plantations situated on opposing ends of a rainfall gradient in southwestern Australia. A strong correlation was observed between the carbon isotope ratio in phloem sap sugars and phloem sap sugar concentration. Carbon isotope discrimination correlated positively with shoot water potential, whereas phloem sap sugar concentration correlated negatively with shoot water potential. The relationship between carbon isotope discrimination measured in phloem sap sugars collected from the stem and c 1 /c a measured instantaneously on subtending leaves was close to that theoretically predicted. Accordingly, a strong, negative relationship was observed between instantaneous c 1 /c a and the phloem sap sugar concentration. Oxygen isotope discrimination in phloem sap sugars also correlated strongly with phloem sap sugar concentration. A theoretical model suggested that the observed variation in stomatal conductance was sufficient to account for the variation observed in oxygen isotope discrimination across the study. Results strongly support the contention that water relations form a mechanistic link between phloem sap sugar concentration and both instantaneous and integrated measures of the

  8. Combustion of pulverized fuel under oxycoal conditions at low oxygen concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Toporov D.; Foerster M.; Kneer R. [RWTH Aachen University, Aachen (Germany). Institute of Heat and Mass Transfer

    2007-07-01

    Oxycoal combustion followed by post-combustion CO{sub 2} sequestration has gained justified interest as an option for significant and relatively quick reduction of emissions from fossil fuel power generation, while taking advantage of the existing power plant infrastructure. Burning pulverised coal in a mixture of CO{sub 2}/O{sub 2} instead of air, however, will lead to modified distributions of temperature, species, and radiation fluxes inside the combustion chamber causing a retroaction on the homogeneous and heterogeneous reactions. Utilizing a burner design, which was optimised for coal combustion in air, for oxycoal combustion will lead to flame instability and poor burnout. Stabilisation of the combustion process can be obtained by: i) an increased oxygen concentration (more than 21% vol.) in the oxidiser mixture, thus achieving similar reaction rates and temperature levels to a pulverised fuel-air flame without significant changes to the flame aerodynamics. ii) modifications to the burner aerodynamics, as presented here. The results in this study are obtained in the frame of OXYCOAL-AC, the research project, having the aim to burn a pulverised coal in a CO{sub 2}/O{sub 2}-atmosphere with oxygen, produced from high-temperature ceramic membrane thus leading to higher efficiency of the whole oxycoal process. Numerical and experimental investigations of a stable oxycoal flame, obtained with {le} 21% oxygen concentration in the burning mixture at the RWTH test facility are reported. Two different burner designs are considered, conclusions concerning the achievement of a stable oxycoal flame at O{sub 2} volume concentrations equal and less to the one of oxygen in air are derived. 8 refs., 7 figs., 1 tab.

  9. Oxygen negative glow: reactive species and emissivity

    International Nuclear Information System (INIS)

    Sahli, Khaled

    1991-01-01

    This research thesis addresses the study of a specific type of oxygen plasma created by electron beams (1 keV, 20 mA/cm"2), negative glow of a luminescent discharge in abnormal regime. The objective is to test the qualities of this plasma as source of two 'active' species of oxygen (singlet molecular oxygen and atomic oxygen) which are useful in applications. The experiment mainly bears on the use of VUV (120 to 150 nm) absorption spectroscopy measurements of concentrations of these both species, and on the recording of plasma emissivity space profiles in the visible region (450 to 850 nm). It appears that low concentrations of singlet oxygen definitely exclude this type of discharge for iodine laser applications. On the contrary, concentrations measured for atomic oxygen show it is a good candidate for the oxidation of large surfaces by sheets of beams. The satisfying comparison of emissivity results with a published model confirm the prevailing role of fast electrons, and gives evidence of an important effect of temperature: temperature can reach 1000 K, and this is in agreement with the presented measurement [fr

  10. Process design and simulation for optimizing the oxygen concentration in Czochralski-grown single-crystal silicon

    International Nuclear Information System (INIS)

    Jung, Y. J.; Kim, W. K.; Jung, J. H.

    2014-01-01

    The highest-concentration impurity in a single-crystal silicon ingot is oxygen, which infiltrates the ingot during growth stage. This oxygen adversely affects the wafer is quality. This study was aimed at finding an optimal design for the Czochralski (Cz) process to enable high-quality and low cost (by reducing power consumption) wafer production by controlling the oxygen concentration in the silicon ingots. In the Cz process, the characteristics of silicon ingots during crystallization are greatly influenced by the design and the configuration of the hot zone, and by crystallization rate. In order to identify process conditions for obtaining an optimal oxygen concentration of 11 - 13 ppma (required for industrial-grade ingots), designed two shield shapes for the hot zone. Furthermore, oxygen concentrations corresponding to these two shapes were compared by evaluating each shape at five different production speeds. In addition, simulations were performed to identify the optimal shield design for industrial applications.

  11. Process design and simulation for optimizing the oxygen concentration in Czochralski-grown single-crystal silicon

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Y. J.; Kim, W. K.; Jung, J. H. [Yeungnam University, Gyeongsan (Korea, Republic of)

    2014-08-15

    The highest-concentration impurity in a single-crystal silicon ingot is oxygen, which infiltrates the ingot during growth stage. This oxygen adversely affects the wafer is quality. This study was aimed at finding an optimal design for the Czochralski (Cz) process to enable high-quality and low cost (by reducing power consumption) wafer production by controlling the oxygen concentration in the silicon ingots. In the Cz process, the characteristics of silicon ingots during crystallization are greatly influenced by the design and the configuration of the hot zone, and by crystallization rate. In order to identify process conditions for obtaining an optimal oxygen concentration of 11 - 13 ppma (required for industrial-grade ingots), designed two shield shapes for the hot zone. Furthermore, oxygen concentrations corresponding to these two shapes were compared by evaluating each shape at five different production speeds. In addition, simulations were performed to identify the optimal shield design for industrial applications.

  12. Control systems for the dissolved oxygen concentration in condensate- and feed-water systems in nuclear power plants

    International Nuclear Information System (INIS)

    Mikajiri, Motohiko; Hosaka, Seiichi.

    1981-01-01

    Purpose: To surely prevent the generation of corrosion products and contaminations in the systems thereby decreasing the exposure dose to operators in BWR type nuclear power plants. Constitution: Dissolved oxygen concentration in condensates is measured by a dissolved oxygen concentration meter disposed to the pipeway down stream of the condensator and the measured value is sent to an injection amount control mechanism for heater drain water. The control mechanism controls the injection amount from the injection mechanism that injection heater drain water from a feed-water heater to the liquid phase in the hot wall of the condensator. Thus, heater drawin water at high dissolved oxygen is injected to the condensates in the condensator which is de-airated and reduced with dissolved oxygen concentration, to maintain the dissolved oxygen concentration at a predetermined level, whereby stable oxide films are formed to the inner surface of the pipeways to prevent the generation of corrosion products such as rusts. (Furukawa, Y.)

  13. Microbial respiration and gene expression as a function of very low oxygen concentration

    DEFF Research Database (Denmark)

    Tiano, Laura

    and denitrification, were only partially described. In spite of the importance of aerobic respiration as a key process in the global carbon cycle, the available data are still few, and highly biased with respect to season, latitude and depth. The main aims of this Ph.D were to: i) develop and test a highly...... to pure cultures (Manuscript III), in order to assess the response of three species of NOB (Nitrospira defluvvi, N. moscoviensis and Nitrospina gracilis) to low O2 concentrations, and the oxygen regulation on the expression of the terminal oxidases genes in N.moscoviensis. The oxygen affinities...... of these pure cultures were lower than found for natural communities of NOB (apparent Km values~ 1- 4 µM), but higher than the ones from the well-studied opportunistic NOB Nitrobacter. The expression of high-affinity terminal oxidases in these NOB could, however, not be confirmed. Overall the results of this Ph...

  14. Role of oxygen concentration distribution and microstructure in luminescent properties of laser-irradiated silicon

    International Nuclear Information System (INIS)

    Zhu, Min; Li, Xiaohong; Li, Guoqiang; Xie, Changxin; Qiu, Rong; Li, Jiawen; Huang, Wenhao

    2015-01-01

    Graphical abstract: Photoluminescence (PL) of monocrystalline silicon irradiated by femtosecond laser pulses was studied. The visible blue luminescence is observed both from the deionized water and air. The position and shape of emission luminescence peaks in the visible range are same at 330 nm. The PL is confirmed to be not merely induced by the oxygen defects or quantum confinement effects, but is commonly decided by the concentration distribution of SiO x and the depth of the surface microstructure. The PL gets strongest only when depth of the surface microstructure is not deeper and the distribution of the shallow SiO x is more intensive. - Highlights: • Different morphologies and compositions of the surface microstructures are formed. • The SiO x concentration and surface microstructure depth commonly decide the PL. • The PL intensity can be controlled by changing the experimental conditions. - Abstract: We study the photoluminescence (PL) of monocrystalline silicon irradiated by femtosecond laser pulses in different environments (deionized water and air) and energy intensities. The fluorescence spectroscopy measurement results indicate that the visible blue luminescence is observed both from the silicon surfaces ablated in the deionized water and air. The more interesting phenomenon is that the position and shape of the emission luminescence peaks in the visible range are substantially the same at the same excitation wavelength 330 nm. Compared with the granular-like microstructure generated on the silicon surface in air, the smaller and stripe-like microstructure is formed in the deionized water as the field emission scanning electron microscope (FESEM) measures. The results of the energy dispersive spectroscopy (EDS) show that silicon and oxygen is the main elemental composition on laser-induced silicon surfaces, and the oxygen content on the sample surfaces formed in air is nearly four times more than that in the deionized water. The studies confirm

  15. Plasma ATP concentration and venous oxygen content in the forearm during dynamic handgrip exercise

    Directory of Open Access Journals (Sweden)

    Askew Christopher D

    2009-12-01

    Full Text Available Abstract Background It has been proposed that adenosine triphosphate (ATP released from red blood cells (RBCs may contribute to the tight coupling between blood flow and oxygen demand in contracting skeletal muscle. To determine whether ATP may contribute to the vasodilatory response to exercise in the forearm, we measured arterialised and venous plasma ATP concentration and venous oxygen content in 10 healthy young males at rest, and at 30 and 180 seconds during dynamic handgrip exercise at 45% of maximum voluntary contraction (MVC. Results Venous plasma ATP concentration was elevated above rest after 30 seconds of exercise (P Conclusions Collectively these results indicate that ATP in the plasma originated from the muscle microcirculation, and are consistent with the notion that deoxygenation of the blood perfusing the muscle acts as a stimulus for ATP release. That ATP concentration was elevated just 30 seconds after the onset of exercise also suggests that ATP may be a contributing factor to the blood flow response in the transition from rest to steady state exercise.

  16. Steady-state ozone concentration in radiation induced noble gas-oxygen discharges

    International Nuclear Information System (INIS)

    Elsayed-Ali, H.E.; Miley, G.H.

    1985-01-01

    Measurements of steady-state ozone concentrations in continuous radiation induced noble gas-O 2 and noble gas-O 2 -SF 6 mixtures has been accomplished. The discharges were created through the bombardment of the gases with energetic particles from the boron-10 (n,α) lithium-7 nuclear reaction. Three noble gases were studied, He, Ne, and Ar at partial pressures of few hundred Torr. The dose rates studied were in the order of 10 15 eV.cm -3 .s -1 . The experimental apparatus and proceedure were previously described. The experimentally observed stead-state ozone concentrations in noble gas-O 2 discharges were about an order of magnitude lower than that observed for oxygen radiolysis at similar dose rates. These results were physically explained by an enhanced role of negative ionic reactions with ozone causing its destruction. In noble gas-O 2 -SF 6 mixtures, the steady-state ozone concentrations were found to be significantly higher (3-6 times) than that without the SF 6 addition. This observation was contrary to only a small increase observed after SF 6 addition to a few hundred Torr oxygen and is explained by an enhanced rate of electron dissociative attachment of ozone in noble gas-O 2 discharges

  17. Steady-state ozone concentrations in radiation induced noble gas-oxygen discharges

    International Nuclear Information System (INIS)

    Elsayed-Ali, H.E.; Miley, G.H.

    1985-01-01

    Measurements of steady-state ozone concentrations in continuous radiation induced noble gas-O/sub 2/ and noble gas-o/sub 2/-SF/sub 6/ mixtures has been accomplished. The discharges were created through the bombardment of the gases with energetic particles from the boron-10 (n,α) lithium-7 nuclear reaction. Three noble gases were studied, He, Ne, and Ar at partial pressures of few hundred Torr. The dose rates studied were in the order of 10/sup 15/ eV . cm/sup -3/ . s/sup -1/. The experimental apparatus and procedure were previously described. The experimentally observed steady-state ozone concentrations in noble gas-O/sub 2/ discharges were about an order of magnitude lower than that observed for oxygen radiolysis at similar dose rates. These results were physically explained by an enhanced role of negative ionic reactions with ozone causing its destruction. In noble gas-O/sub 2/-SF/sub 6/ mixtures, the steady-state ozone concentrations were found to be significantly higher (3-6 times) than that without the SF/sub 6/ addition. This observation was contrary to only a small increase observed after SF/sub 6/ addition to a few hundred Torr oxygen and is explained by an enhanced rate of electron dissociative attachment of ozone in noble gas-O/sub 2/ discharges

  18. Oxygen concentration modulates cellular senescence and autophagy in human trophoblast cells.

    Science.gov (United States)

    Seno, Kotomi; Tanikawa, Nao; Takahashi, Hironori; Ohkuchi, Akihide; Suzuki, Hirotada; Matsubara, Shigeki; Iwata, Hisataka; Kuwayama, Takehito; Shirasuna, Koumei

    2018-02-15

    We investigated the effect of oxygen concentrations on cellular senescence and autophagy and examined the role of autophagy in human trophoblast cells. Human first-trimester trophoblast cells (Sw.71) were incubated under 21%, 5%, or 1% O 2 concentrations for 24 hours. We examined the extent of senescence caused using senescence-associated β-galactosidase (SA-β-Gal) and senescence-associated secretory phenotype (SASP) as markers. Moreover, we examined the role of autophagy in causing cellular senescence using an autophagy inhibitor (3-methyladenine, 3MA). Physiological normoxia (5% O 2 ) decreased SA-β-Gal-positive cells and SASP including interleukin-6 (IL-6) and IL-8 compared with cultured cells in 21% O 2 . Pathophysiological hypoxia (1% O 2 ) caused cytotoxicity, including extracellular release of ATP and lactate dehydrogenase, and decreased senescence phenotypes. 3MA-treated trophoblast cells significantly suppressed senescence markers (SA-β-Gal-positive cells and SASP secretion) in O 2 -independent manner. We conclude that O 2 concentration modulates cellular senescence phenotypes regulating autophagy in the human trophoblast cells. Moreover, inhibiting autophagy suppresses cellular senescence, suggesting that autophagy contributes to oxygen stress-induced cellular senescence. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  19. Image analyzing method to evaluate in situ bioluminescence from an obligate anaerobe cultivated under various dissolved oxygen concentrations.

    Science.gov (United States)

    Ninomiya, Kazuaki; Yamada, Ryuji; Matsumoto, Masami; Fukiya, Satoru; Katayama, Takane; Ogino, Chiaki; Shimizu, Nobuaki

    2013-02-01

    An image analyzing method was developed to evaluate in situ bioluminescence expression, without exposing the culture sample to the ambient oxygen atmosphere. Using this method, we investigated the effect of dissolved oxygen concentration on bioluminescence from an obligate anaerobe Bifidobacterium longum expressing bacterial luciferase which catalyzes an oxygen-requiring bioluminescent reaction. Copyright © 2012 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  20. Preservation of high glycolytic phenotype by establishing new acute lymphoblastic leukemia cell lines at physiologic oxygen concentration.

    Science.gov (United States)

    Sheard, Michael A; Ghent, Matthew V; Cabral, Daniel J; Lee, Joanne C; Khankaldyyan, Vazgen; Ji, Lingyun; Wu, Samuel Q; Kang, Min H; Sposto, Richard; Asgharzadeh, Shahab; Reynolds, C Patrick

    2015-05-15

    Cancer cells typically exhibit increased glycolysis and decreased mitochondrial oxidative phosphorylation, and they continue to exhibit some elevation in glycolysis even under aerobic conditions. However, it is unclear whether cancer cell lines employ a high level of glycolysis comparable to that of the original cancers from which they were derived, even if their culture conditions are changed to physiologically relevant oxygen concentrations. From three childhood acute lymphoblastic leukemia (ALL) patients we established three new pairs of cell lines in both atmospheric (20%) and physiologic (bone marrow level, 5%) oxygen concentrations. Cell lines established in 20% oxygen exhibited lower proliferation, survival, expression of glycolysis genes, glucose consumption, and lactate production. Interestingly, the effects of oxygen concentration used during cell line initiation were only partially reversible when established cell cultures were switched from one oxygen concentration to another for eight weeks. These observations indicate that ALL cell lines established at atmospheric oxygen concentration can exhibit relatively low levels of glycolysis and these levels are semi-permanent, suggesting that physiologic oxygen concentrations may be needed from the time of cell line initiation to preserve the high level of glycolysis commonly exhibited by leukemias in vivo. Copyright © 2015. Published by Elsevier Inc.

  1. Effect of SO2 concentration on polyphenol development during red wine micro-oxygenation.

    Science.gov (United States)

    Tao, Jianxiong; Dykes, Stuart I; Kilmartin, Paul A

    2007-07-25

    A Merlot wine in 15 L research tanks was subjected to micro-oxygenation at 10 mL O2 per liter of wine per month over a 16 week period with additions of 0, 50, 100, and 200 mg/L SO2. A large decrease in monomeric anthocyanins and flavan-3-ols was seen in wines with a lower concentration of SO2, coupled with an increase in nonbleachable pigments; an increase in tannin, measured using precipitation with methyl cellulose; and a greater size and red coloration of a proanthocyanidin extract obtained using Sephadex LH-20. These changes were largely suppressed in wines initially treated with 200 mg/L SO2 and occurred more slowly in wines stored in bottles in the absence of O2. The concentration of SO2 is shown to regulate the polyphenol chemistry involved in the formation of polymeric pigments and changes in tannin structure affecting wine astringency.

  2. Corrosion behavior of steels in liquid lead bismuth with low oxygen concentrations

    Science.gov (United States)

    Kurata, Yuji; Futakawa, Masatoshi; Saito, Shigeru

    2008-02-01

    Corrosion tests in pots were conducted to elucidate corrosion behavior of various steels in liquid lead-bismuth for 3000 h under the condition of an oxygen concentration of 5 × 10 -8 wt% at 450 °C and an oxygen concentration of 3 × 10 -9 wt% at 550 °C, respectively. Significant corrosion was not observed at 450 °C for ferritic/martensitic steels, F82H, Mod.9Cr-1Mo steel, 410SS, 430SS except 2.25Cr-1Mo steel. Pb-Bi penetration into steels and dissolution of elements into Pb-Bi were severe at 550 °C even for ferritic/martensitic steels. Typical dissolution attack occurred for pure iron both at 550 °C without surface Fe 3O 4 and at 450 °C with a thin Fe 3O 4 film. Ferritization due to dissolution of Ni and Cr, and Pb-Bi penetration were recognized for austenitic stainless steels, 316SS and 14Cr-16Ni-2Mo steel at both temperatures of 450 °C and 550 °C. The phenomena were mitigated for 18Cr-20Ni-5Si steel. In some cases oxide films could not be a corrosion barrier in liquid lead-bismuth.

  3. The design of a PC-based real-time system for monitoring Methane and Oxygen concentration in biogas production

    Science.gov (United States)

    Yantidewi, M.; Muntini, M. S.; Deta, U. A.; Lestari, N. A.

    2018-03-01

    Limited fossil fuels nowadays trigger the development of alternative energy, one of which is biogas. Biogas is one type of bioenergy in the form of fermented gases of organic materials such as animal waste. The components of gases present in biogas and affect the biogas production are various, such as methane and oxygen. The biogas utilization will be more optimal if both gases concentration (in this case is methane and oxygen concentration) can be monitored. Therefore, this research focused on designing the monitoring system of methane and oxygen concentration in biogas production in real-time. The results showed that the instrument system was capable of monitoring and recording the data of gases (methane and oxygen) concentration in biogas production in every second.

  4. Physiology of Aspergillus niger in Oxygen-Limited Continuous Cultures: Influence of Aeration, Carbon Source Concentration and Dilution Rate

    DEFF Research Database (Denmark)

    Diano, Audrey; Peeters, J.; Dynesen, Jens Østergaard

    2009-01-01

    In industrial production of enzymes using the filamentous fungus Aspergilhis niger supply of sufficient oxygen is often a limitation, resulting in the formation of by-products such as polyols. In order to identify the mechanisms behind formation of the different by-products we studied the effect...... of low oxygen availability, at different carbon source concentrations and at different specific growth rates, on the metabolism of A. niger, using continuous cultures. The results show that there is an increase in the production of tricarboxylic acid (TCA) cycle intermediates at low oxygen concentrations...

  5. Influences of dissolved oxygen concentration on biocathodic microbial communities in microbial fuel cells.

    Science.gov (United States)

    Rago, Laura; Cristiani, Pierangela; Villa, Federica; Zecchin, Sarah; Colombo, Alessandra; Cavalca, Lucia; Schievano, Andrea

    2017-08-01

    Dissolved oxygen (DO) at cathodic interface is a critical factor influencing microbial fuel cells (MFC) performance. In this work, three MFCs were operated with cathode under different DO conditions: i) air-breathing (A-MFC); ii) water-submerged (W-MFC) and iii) assisted by photosynthetic microorganisms (P-MFC). A plateau of maximum current was reached at 1.06±0.03mA, 1.48±0.06mA and 1.66±0.04mA, increasing respectively for W-MFC, P-MFC and A-MFC. Electrochemical and microbiological tools (Illumina sequencing, confocal microscopy and biofilm cryosectioning) were used to explore anodic and cathodic biofilm in each MFC type. In all cases, biocathodes improved oxygen reduction reaction (ORR) as compared to abiotic condition and A-MFC was the best performing system. Photosynthetic cultures in the cathodic chamber supplied high DO level, up to 16mg O2 L -1 , which sustained aerobic microbial community in P-MFC biocathode. Halomonas, Pseudomonas and other microaerophilic genera reached >50% of the total OTUs. The presence of sulfur reducing bacteria (Desulfuromonas) and purple non-sulfur bacteria in A-MFC biocathode suggested that the recirculation of sulfur compounds could shuttle electrons to sustain the reduction of oxygen as final electron acceptor. The low DO concentration limited the cathode in W-MFC. A model of two different possible microbial mechanisms is proposed which can drive predominantly cathodic ORR. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Alveolar and serum concentrations of imipenem in two lung transplant recipients supported with extracorporeal membrane oxygenation.

    Science.gov (United States)

    Welsch, C; Augustin, P; Allyn, J; Massias, L; Montravers, P; Allou, N

    2015-02-01

    Venovenous extracorporeal membrane oxygenation (ECMO) is increasingly used in patients with respiratory failure who fail conventional treatment. Postoperative pneumonia is the most common infection after lung transplantation (40%). Imipenem is frequently used for empirical treatment of nosocomial pneumonia in the intensive care unit. Nevertheless, few data are available on the impact of ECMO on pharmacokinetics, and no data on imipenem dosing during ECMO. Currently, no guidelines exist for antibiotic dosing during ECMO support. We report the cases of 2 patients supported with venovenous ECMO for refractory acute respiratory distress syndrome following single lung transplantation for pulmonary fibrosis, treated empirically with 1 g of imipenem intravenously every 6 h. Enterobacter cloacae was isolated from the respiratory sample of Patient 1 and Klebsiella pneumoniae was isolated from the respiratory sample of Patient 2. Minimum inhibitory concentrations of the 2 isolated strains were 0.125 and 0.25 mg/L, respectively. Both patients were still alive on day 28. This is the first report, to our knowledge, of imipenem concentrations in lung transplantation patients supported with ECMO. This study confirms high variability in imipenem trough concentrations in patients on ECMO and with preserved renal function. An elevated dosing regimen (4 g/24 h) is more likely to optimize drug exposure, and therapeutic drug monitoring is recommended, where available. Population pharmacokinetic studies are indicated to develop evidence-based dosing guidelines for ECMO patients. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  7. Validation of NIRS in measuring tissue hemoglobin concentration and oxygen saturation on ex vivo and isolated limb models

    Science.gov (United States)

    Xu, Xiaorong; Zhu, Wen; Padival, Vikram; Xia, Mengna; Cheng, Xuefeng; Bush, Robin; Christenson, Linda; Chan, Tim; Doherty, Tim; Iatridis, Angelo

    2003-07-01

    Photonify"s tissue spectrometer uses Near-Infrared Spectroscopy for real-time, noninvasive measurement of hemoglobin concentration and oxygen saturation [SO2] of biological tissues. The technology was validated by a series of ex vivo and animal studies. In the ex vivo experiment, a close loop blood circulation system was built, precisely controlling the oxygen saturation and the hemoglobin concentration of a liquid phantom. Photonify"s tissue spectrometer was placed on the surface of the liquid phantom for real time measurement and compared with a gas analyzer, considered the gold standard to measure oxygen saturation and hemoglobin concentration. In the animal experiment, the right hind limb of each dog accepted onto the study was surgically removed. The limb was kept viable by connecting the femoral vein and artery to a blood-primed extracorporeal circuit. Different concentrations of hemoglobin were obtained by adding designated amount of saline solution into the perfusion circuit. Photonify"s tissue spectrometers measured oxygen saturation and hemoglobin concentration at various locations on the limb and compared with gas analyzer results. The test results demonstrated that Photonify"s tissue spectrometers were able to detect the relative changes in tissue oxygen saturation and hemoglobin concentration with a high linear correlation compared to the gas analyzer

  8. Optical measurements of atomic oxygen concentration, temperature and nitric oxide production rate in flames

    Science.gov (United States)

    Myhr, Franklin Henry

    An optical method for measuring nitric oxide (NO) production rates in flames was developed and characterized in a series of steady, one-dimensional, atmospheric-pressure laminar flames of 0.700 Hsb2/0.199 Nsb2/0.101 COsb2 or 0.700 CHsb4/0.300 Nsb2 (by moles) with dry air, with equivalence ratios from 0.79 to 1.27. Oxygen atom concentration, (O), was measured by two-photon laser-induced fluorescence (LIF), temperature was measured by ultraviolet Rayleigh scattering, and nitrogen concentration was calculated from supplied reactant flows; together this information was used to calculate the NO production rate through the thermal (Zel'dovich) mechanism. Measurements by two other techniques were compared with results from the above method. In the first comparison, gas sampling was used to measure axial NO concentration profiles, the slopes of which were multiplied by velocity to obtain total NO production rates. In the second comparison, LIF measurements of hydroxyl radical (OH) were used with equilibrium water concentrations and a partial equilibrium assumption to find (O). Nitric oxide production rates from all three methods agreed reasonably well. Photolytic interference was observed during (O) LIF measurements in all of the flames; this is the major difficulty in applying the optical technique. Photolysis of molecular oxygen in lean flames has been well documented before, but the degree of interference observed in the rich flames suggests that some other molecule is also dissociating; the candidates are OH, CO, COsb2 and Hsb2O. An extrapolative technique for removing the effects of photolysis from (O) LIF measurements worked well in all flames where NO production was significant. Using the optical method to measure NO production rates in turbulent flames will involve a tradeoff among spatial resolution, systematic photolysis error, and random shot noise. With the conventional laser system used in this work, a single pulse with a resolution of 700 mum measured NO

  9. MANAGEMENT PROCESS OF CULTIVATION OF MICROORGANISMS ON DYNAMICS OF TEMPERATURE OF A BIOMASS AND CONCENTRATION OF OXYGEN IN EXHAUST GASES

    Directory of Open Access Journals (Sweden)

    B. A. Golodenko

    2012-01-01

    Full Text Available On an example of industrial production of baking yeast the way of automatic control of process of cultivation of microorganisms is stated. The way provides management of aeration of a biomass on the set speed of change of its concentration and temperatures in view of speed of change of concentration of oxygen in the fulfilled gases.

  10. Real time continuous oxygen concentration monitoring system during malaxation for the production of Virgin Olive Oil

    Directory of Open Access Journals (Sweden)

    Aiello, G.

    2012-10-01

    Full Text Available During the mechanical extraction process of Virgin Olive Oil (VOO some important physical phenomena and enzymatic transformations occur which influence the quality of the final product. The control of process parameters is crucial to ensure the quality of VOO, therefore process monitoring and control is a fundamental requirement in the modern VOO processing industry. The present work proposes an innovative Real-Time Monitoring System (RTMS aimed at continuously measuring the oxygen concentration during the malaxation process in order to establish a correlation with the quality of the final product obtained. This monitoring system is based on an oxygen concentration sensor directly connected to the malaxation chamber and a data acquisition system to analyze and store the measured values in a process database. The experimental results obtained show that the use of oxygen during malaxation improves some qualitative parameters of VOO such as free fatty acids and total polyphenols while others (peroxide values and spectrophotometric indexes worsen. These results are similar to those obtained by employing nitrogen, which is the traditional technique to avoid the wellknown oxidation processes studied by several researchers, thus demonstrating that the presence of oxygen during the malaxation process can have beneficial effects on the quality of VOO when its concentration is properly controlled.

    Durante el proceso de extracción mecánica del aceite de oliva virgen ocurren importantes fenómenos físicos y transformaciones enzimáticas que influyen en la calidad del producto final. El control de los parámetros del proceso es crucial para garantizar la calidad del aceite de oliva virgen, por tanto la monitorización y el control del proceso son requisitos fundamentales en el moderno tratamiento industrial del aceite de oliva virgen. El presente trabajo propone un sistema de monitorización innovador en tiempo real dirigido a medir continuamente

  11. Effects of diagenesis on strontium, carbon, nitrogen and oxygen concentration and isotopic composition of bone

    Science.gov (United States)

    Nelson, Bruce K.; Deniro, Michael J.; Schoeninger, Margaret J.; De Paolo, Donald J.; Hare, P. E.

    1986-09-01

    Paleodietary analysis based on variations in the trace element and stable isotopic composition of inorganic and organic phases in fossil bone depends on the assumption that measured values reflect in vivo values. To test for postmortem alteration, we measured 87Sr /86Sr , 13C /12C , 18O /16O and 15N /14N ratios and Sr concentrations in modern and prehistoric (610 to 5470 yr old) bones of animals with marine or terrestrial diets from Greenland. Bones from modern terrestrial feeders have substantially lower Sr concentrations and more radiogenic 87Sr /86Sr ratios than those from modern marine feeders. This contrast was not preserved in the prehistoric samples, which showed almost complete overlap for both Sr concentration and isotopic composition in bones from the two types of animals. Leaching experiments, X-ray diffraction analysis and infrared spectroscopy indicate that alteration of the Sr concentration and isotopic composition in prehistoric bone probably results from nearly complete exchange with groundwater. Oxygen isotope ratios in fossil apatite carbonate also failed to preserve the original discrimination between modern terrestrial and marine feeders. The C isotope ratio of apatite carbonate did not discriminate between animals with marine or terrestrial diets in the modern samples. Even so, the ranges of apatite δ 13C values in prehistoric bone are more scattered than in modern samples for both groups, suggesting alteration had occurred. δ 13C and δ 15N values of collagen in modern bone are distinctly different for the two feeding types, and this distinction is preserved in most of the prehistoric samples. Our results suggest that postmortem alteration of dietary tracers in the inorganic phases of bone may be a problem at all archaeological sites and must be evaluated in each case. While collagen analyzed in this study was resistant to alteration, evaluation of the possibility of diagenetic alteration of its isotopic composition in bones from other

  12. Testing the fidelity of laminations as a proxy for oxygen concentration in the Bering Sea over millennial to orbital timescales

    Science.gov (United States)

    Black, A. E.; Baranow, N.; Amdur, S.; Cook, M. S.

    2017-12-01

    Ocean circulation and biological productivity play an important role in the climate system through their contribution to global heat transport and air-sea exchange of CO­2. Oceanic oxygen concentration provides insight to ocean circulation and biological productivity. Sediment laminations provide a valuable proxy for local oceanic oxygen concentration. Many sediment cores from the Pacific Ocean are laminated from the last deglaciation, but previous studies have not provided an in-depth examination of laminations over many glacial and interglacial (G/IG) cycles. Typically, studies to date that consider bioturbation as a proxy for oxygen concentration have only considered one sediment core from a site, leaving ambiguity as to whether laminations faithfully record local oxygen levels. With sediment cores from three different holes (A, C, D) on the northern Bering Slope from IODP site U1345 (1008m), we investigate how faithfully laminations record oxygen concentration. We assign a bioturbation index from 1 to 4 for 1-cm intervals for the cores from each of the three holes and align the holes based on physical properties data. We find that the bioturbation is relatively consistent (within one bioturbation unit) between holes, suggesting that laminations may be a faithful, if not perfect, proxy for local oxygen concentration. After examining laminations from a complete hole, representing over 500,000 years, there seems to be no consistent pattern of laminations during the past five glacial cycles, suggesting there is no consistent pattern to oxygen concentration during glacial periods in the northern Bering Slope. Thus, hypotheses on ocean circulation and productivity in the northern Bering Sea from the last deglaciation may not apply to previous G/IG cycles.

  13. Feedforward-feedback control of dissolved oxygen concentration in a predenitrification system.

    Science.gov (United States)

    Yong, Ma; Yongzhen, Peng; Shuying, Wang

    2005-07-01

    As the largest single energy-consuming component in most biological wastewater treatment systems, aeration control is of great interest from the point of view of saving energy and improving wastewater treatment plant efficiency. In this paper, three different strategies, including conventional constant dissolved oxygen (DO) set-point control, cascade DO set-point control, and feedforward-feedback DO set-point control were evaluated using the denitrification layout of the IWA simulation benchmark. Simulation studies showed that the feedforward-feedback DO set-point control strategy was better than the other control strategies at meeting the effluent standards and reducing operational costs. The control strategy works primarily by feedforward control based on an ammonium sensor located at the head of the aerobic process. It has an important advantage over effluent measurements in that there is no (or only a very short) time delay for information; feedforward control was combined with slow feedback control to compensate for model approximations. The feedforward-feedback DO control was implemented in a lab-scale wastewater treatment plant for a period of 60 days. Compared to operation with constant DO concentration, the required airflow could be reduced by up to 8-15% by employing the feedforward-feedback DO-control strategy, and the effluent ammonia concentration could be reduced by up to 15-25%. This control strategy can be expected to be accepted by the operating personnel in wastewater treatment plants.

  14. An fMRI study on variation of visuospatial cognitive performance of young male due to highly concentrated oxygen administration

    Science.gov (United States)

    Chung, Soon Cheol; Kim, Ik Hyeon; Tack, Gye Rae; Sohn, Jin Hun

    2004-04-01

    This study investigated the effects of 30% oxygen administration on the visuospatial cognitive performance using fMRI. Eight college students (right-handed, average age 23.5) were selected as subjects for this study. Oxygen supply equipment which gives 21% and 30% oxygen at a constant rate of 8L/min was developed for this study. To measure the performance of visuospatial cognition, two questionnaires with similar difficulty containing 20 questions each were also developed. Experiment was designed as two runs: run for visuospatial cognition test with normal air (21% of oxygen) and run for visuospatial cognition test with highly concentrated air (30% of oxygen). Run consists of 4 blocks and each block has 8 control problems and 5 visuospatial problems. Functional brain images were taken from 3T MRI using single-shot EPI method. Activities of neural network due to performing visuospatial cognition test were identified using subtraction procedure, and activation areas while performing visuospatial cognition test were extracted using double subtraction procedure. Activities were observed at occipital lobe, parietal lobe, and frontal lobe when performing visuospatial cognition test following both 21% and 30% oxygen administration. But in case of only 30% oxygen administration there were more activities at left precuneus, left cuneus, right postcentral gyrus, bilateral middle frontal gyri, right inferior frontal gyrus, left superior frontal gyrus, bilateral uvula, bilateral pyramis, and nodule compared with 21% oxygen administration. From results of visuospatial cognition test, accuracy rate increased in case of 30% oxygen administration. Thus it could be concluded that highly concentrated oxygen administration has positive effects on the visuospatial cognitive performance.

  15. A spin exchange model for singlet fission

    Science.gov (United States)

    Yago, Tomoaki; Wakasa, Masanobu

    2018-03-01

    Singlet fission has been analyzed with the Dexter model in which electron exchange occurs between chromophores, conserving the spin for each electron. In the present study, we propose a spin exchange model for singlet fission. In the spin exchange model, spins are exchanged by the exchange interaction between two electrons. Our analysis with simple spin functions demonstrates that singlet fission is possible by spin exchange. A necessary condition for spin exchange is a variation in exchange interactions. We also adapt the spin exchange model to triplet fusion and triplet energy transfer, which often occur after singlet fission in organic solids.

  16. Determination of respiration rates in water with sub-micromolar oxygen concentrations

    Directory of Open Access Journals (Sweden)

    Emilio Garcia-Robledo

    2016-11-01

    Full Text Available It is crucial for our study and understanding of element transformations in low-oxygen waters that we are able to reproduce the in situ conditions during laboratory incubations to an extent that does not result in unacceptable artefacts. In this study we have explored how experimental conditions affect measured rates of O2 consumption in low-O2 waters from the anoxic basin of Golfo Dulce (Costa Rica and oceanic waters off Chile-Peru. High-sensitivity optode dots placed within all-glass incubation containers allowed for high resolution O2 concentration measurements in the nanomolar and low µmolar range and thus also for the determination of rates of oxygen consumption by microbial communities. Consumption rates increased dramatically (from 3 and up to 60 times by prolonged incubations, and started to increase after 4-5 hours in surface waters and after 10-15 h in water from below the upper mixed layer. Estimated maximum growth rates during the incubations suggest the growth of opportunistic microorganism with doubling times as low as 2.8 and 4.6 h for the coastal waters of Golfo Dulce (Costa Rica and oceanic waters off Chile and Peru, respectively. Deoxygenation by inert gas bubbling led to increases in subsequently determined rates, possibly by liberation of organics from lysis of sensitive organisms, particle or aggregate alterations or other processes mediated by the strong turbulence. Stirring of the water during the incubation led to an about 50% increase in samples previously deoxygenated by bubbling, but had no effect in untreated samples. Our data indicate that data for microbial activity obtained by short incubations of minimally manipulated water are most reliable, but deoxygenation is a prerequisite for many laboratory experiments, such as determination of denitrification rates, as O2 contamination by sampling is practically impossible to avoid.

  17. Catalyst evaluation for oxygen reduction reaction in concentrated phosphoric acid at elevated temperatures

    Science.gov (United States)

    Hu, Yang; Jiang, Yiliang; Jensen, Jens Oluf; Cleemann, Lars N.; Li, Qingfeng

    2018-01-01

    Phosphoric acid is the common electrolyte for high-temperature polymer electrolyte fuel cells (HT-PEMFCs) that have advantages such as enhanced CO tolerance and simplified heat and water management. The currently used rotating disk electrode technique is limited to tests in dilute solutions at low temperatures and hence is not suitable for catalyst evaluation for HT-PEMFCs. In this study, we have designed and constructed a half-cell setup to measure the intrinsic activities of catalysts towards the oxygen reduction reaction (ORR) in conditions close to HT-PEMFC cathodes. By optimization of the hydrophobic characteristics of electrodes and the catalyst layer thickness, ORR activities of typical Pt/C catalysts are successfully measured in concentrated phosphoric acid at temperatures above 100 °C. In terms of mass-specific activities, the catalyst exhibits about two times higher activity in the half-cell electrode than that observed in fuel cells, indicating the feasibility of the technique as well as the potential for further improvement of fuel cell electrode performance.

  18. Thermodynamic Analysis of Oxygen-Enriched Direct Smelting of Jamesonite Concentrate

    Science.gov (United States)

    Zhang, Zhong-Tang; Dai, Xi; Zhang, Wen-Hai

    2017-12-01

    Thermodynamic analysis of oxygen-enriched direct smelting of jamesonite concentrate is reported in this article. First, the occurrence state of lead, antimony and other metallic elements in the smelting process was investigated theoretically. Then, the verification test was carried out. The results indicate that lead and antimony mainly exist in the alloy in the form of metallic lead and metallic antimony. Simultaneously, lead and antimony were also oxidized into the slag in the form of lead-antimony oxide. Iron and copper could be oxidized into the slag in the form of oxides in addition to combining with antimony in the alloy, while zinc was mainly oxidized into the slag in the form of zinc oxide. The verification test indicates that the main phases in the alloy contain metallic lead, metallic antimony and a small amount of Cu2Sb, FeSb2 intermetallic compounds, and the slag is mainly composed of kirschsteinite, fayalite and zinc oxide, in agreement with the thermodynamic analysis.

  19. Control of oxygen vacancies and Ce+3 concentrations in doped ceria nanoparticles via the selection of lanthanide element

    International Nuclear Information System (INIS)

    Shehata, N.; Meehan, K.; Hudait, M.; Jain, N.

    2012-01-01

    The effect of lanthanides that have positive association energies with oxygen vacancies, such as samarium and neodymium, and the elements with negative association energies, such as holmium and erbium, on ionization state of cerium and, consequentially, the oxygen vacancy concentration in doped ceria nanoparticles are investigated in this article. Structural and optical characterizations of the doped and undoped ceria nanoparticles, synthesized using chemical precipitation, are carried out using transmission electron microscopy, X-ray diffractometry, optical absorption spectroscopy, and fluorescence spectroscopy. It is deduced that the negative association energy dopants decrease the conversion of Ce +4 into Ce +3 and, hence, scavenge the oxygen vacancies, evidenced by the observed increase in the allowed direct bandgap, decrease in the integrated fluorescence intensity, and increased the size of doped nanoparticles. The opposite trends are obtained when the positive association dopants are used. It is concluded that the determining factor as to whether a lanthanide dopant in ceria acts as a generator or scavenger of oxygen vacancies in ceria nanoparticles is the sign of the association energy between the element and the oxygen vacancies. The ability to tailor the ionization state of cerium and the oxygen vacancy concentration in ceria has applications in a broad range of fields, which include catalysis, biomedicine, electronics, and environmental sensing.

  20. Radiative lifetime measurements of the singlet-G states of H2 and the 4p35p and 4d5D0 states of neutral oxygen atom

    International Nuclear Information System (INIS)

    Day, R.L.

    1981-01-01

    The present work reports measurements of the mean radiative lifetime for the G 1 μ/sub g/ + (v' = 0,1,2,3) and l 1 II/sub g/ + (v' = 0) Rydberg states and the K 1 μ/sub g/ + (v' = 0,1,2),M 1 μ/sub g/ + (v' = 0) and N 1 μ/sub g/ + (v' - 1,2) doubly excited of the H 2 molecule. In particular, the resulting radiative transitions G 1 μ/sub g/ + (v' = 0,1,2,3) → B 1 μ/sub u/ + (v'' = 0,1,3,5,7), l 1 II/sub g/ + (v' = 0) → B 1 μ/sub u/ + (v'' = 0), K 1 μ/sub g/ + (v' = 0,1,2) → B 1 μ/sub u/ + (v'' = 0,1), M 1 μ/sub g/ + (v' = 0) → B 1 μ/sub u/ + (v'' = 0) and N 1 μ/sub g/ + (v' = 1,2) → B 1 μ/sub u/ + (v'' = 0,2) are observed using time-resolved techniques. Radiative lifetime measurements in the range approx. 21 to 70 ns are obtained at 50 eV incident electron energy and approx. 30 mtorr H 2 gas pressure. In addition, H 2 - H 2 * quenching rate data are obtained for several rovibronic levels of the singlet-g states over the pressure range approx. 10 to 400 mtorr. In addition, time-resolved techniques are also used to observe the 4p 5 P → 3s 5 S 0 , 4p 3 P → 3s 3 S 0 , and 4d 5 D 0 → 3p 3 P multiplet transitions of the Ol spectrum occurring at lambda = 3947 A, lambda = 4368 A, and lambda = 6157 A, respectively. The excited atomic states are produced through dissociative-excitation of O 2 target gas by a pulsed electron beam of approx. 0.5 and 2 μs pulse width and 100 eV incident energy. The mean radiative lifetimes of the 4p 5 P, 4p 3 P and 4d 5 D 0 multiplets are obtained from analysis of the resulting radiative decay over the pressure range approx. 20 - 100 mtorr, and are reported as 194 ns, 161 ns, and 95 ns, respectively. The corresponding collisional deactivation cross sections for the multiplets are also obtained from the lifetime versus pressure measurements and are reported as 3.2 x 10 - 15 cm 2 , 7.7 x 10 - 15 cm 2 , and 1.6 x 10 - 15 cm 2 , respectively

  1. Determination of local concentration of H2O molecules and gas temperature in the process of hydrogen – oxygen gas mixture heating by means of linear and nonlinear laser spectroscopy

    International Nuclear Information System (INIS)

    Kozlov, D N; Kobtsev, V D; Stel'makh, O M; Smirnov, Valery V; Stepanov, E V

    2013-01-01

    Employing the methods of linear absorption spectroscopy and nonlinear four-wave mixing spectroscopy using laserinduced gratings we have simultaneously measured the local concentrations of H 2 O molecules and the gas temperature in the process of the H 2 – O 2 mixture heating. During the measurements of the deactivation rates of pulsed-laser excited singlet oxygen O 2 (b 1 Σ + g ) in collisions with H 2 in the range 294 – 850 K, the joint use of the two methods made it possible to determine the degree of hydrogen oxidation at a given temperature. As the mixture is heated, H 2 O molecules are formed by 'dark' reactions of H 2 with O 2 in the ground state. The experiments have shown that the measurements of tunable diode laser radiation absorption along an optical path through the inhomogeneously heated gas mixture in a cell allows high-accuracy determination of the local H 2 O concentration in the O 2 laser excitation volume, if the gas temperature in this volume is known. When studying the collisional deactivation of O 2 (b 1 Σ + g ) molecules, the necessary measurements of the local temperature can be implemented using laser-induced gratings, arising due to spatially periodic excitation of O 2 (X 3 Σ - g ) molecules to the b 1 Σ + g state by radiation of the pump laser of the four-wave mixing spectrometer. (laser spectroscopy)

  2. Concentrations and fluxes of isoprene and oxygenated VOCs at a French Mediterranean oak forest

    International Nuclear Information System (INIS)

    Kalogridis, C.; Gros, V.; Sarda-Esteve, R.; Bonsang, B.; Bonnaire, N.; Boissard, C.; Baisnee, D.; Lathiere, J.

    2014-01-01

    The CANOPEE project aims to better understand the biosphere-atmosphere exchanges of biogenic volatile organic compounds (BVOCs) in the case of Mediterranean ecosystems and the impact of in-canopy processes on the atmospheric chemical composition above the canopy. Based on an intensive field campaign, the objective of our work was to determine the chemical composition of the air inside a canopy as well as the net fluxes of reactive species between the canopy and the boundary layer. Measurements were carried out during spring 2012 at the field site of the Oak Observatory of the Observatoire de Haute Provence (O3HP) located in the southeast of France. The site is a forest ecosystem dominated by downy oak, Quercus pubescens Willd., a typical Mediterranean species which features large isoprene emission rates. Mixing ratios of isoprene, its degradation products methylvinylketone (MVK) and methacrolein (MACR) and several other oxygenated VOC (OxVOC) were measured above the canopy using an online proton transfer reaction mass spectrometer (PTR-MS), and fluxes were calculated by the disjunct eddy covariance approach. The O3HP site was found to be a very significant source of isoprene emissions, with daily maximum ambient concentrations ranging between 2-16 ppbv inside and 2-5 ppbv just above the top of the forest canopy. Significant isoprene fluxes were observed only during daytime, following diurnal cycles with midday net emission fluxes from the canopy ranging between 2.0 and 9.7 mgm -2 h -1 . Net isoprene normalized flux (at 30 C, 1000 μmol quantam -2 s -1 ) was estimated at 7.4 mgm -2 h -1 . Evidence of direct emission of methanol was also found exhibiting maximum daytime fluxes ranging between 0.2 and 0.6 mgm -2 h -1 , whereas flux values for monoterpenes and others OxVOC such as acetone and acetaldehyde were below the detection limit. The MVK+MACR-to-isoprene ratio provided useful information on the oxidation of isoprene, and is in agreement with recent findings

  3. About the 'enlightenment' of nonideal hydrogen-oxygen plasma at a electron concentration Ne19 cm-3

    International Nuclear Information System (INIS)

    Fedorovich, O.A.

    2013-01-01

    The results of experimental determination of the emissivity of the hydrogen-oxygen plasma pulsed discharge in water and their comparison with calculations. It is shown that when concentrations nonideal plasma N e >3 centre dot 10 18 cm -3 , is observed 'enlightenment' of plasma. The reduction of a emitting ability . can be more order in the N e =3 centre dot 10 19 cm -3 and increases with increasing electron concentration.

  4. Colour singlets in perturbative QCD

    International Nuclear Information System (INIS)

    Bassetto, A.

    1979-01-01

    In the axial gauge and at the leading log level, a definite and consistent picture seems to emerge of a parton decay into states in which many partons are found just before confinement should take place. They are grouped into colourless clusters in a number sufficient to exhaust the ''final'' state, still possessing a finite average mass. This result is peculiar of QCD, in particular of its non-abelian nature. Large transverse momenta or more generally average invariant quantities of partons are mainly due to the multiplicities involved in the branching processes. If eventually confinement would convert these clusters into hadrons (and this is of course the main issue which has still to be proven) without a large rearrangement of the colour lines, the picture we have found for colour singlets could apply to the real hadronic world. (author)

  5. Singlet fission in pentacene dimers

    Science.gov (United States)

    Zirzlmeier, Johannes; Lehnherr, Dan; Coto, Pedro B.; Chernick, Erin T.; Casillas, Rubén; Basel, Bettina S.; Thoss, Michael; Tykwinski, Rik R.; Guldi, Dirk M.

    2015-01-01

    Singlet fission (SF) has the potential to supersede the traditional solar energy conversion scheme by means of boosting the photon-to-current conversion efficiencies beyond the 30% Shockley–Queisser limit. Here, we show unambiguous and compelling evidence for unprecedented intramolecular SF within regioisomeric pentacene dimers in room-temperature solutions, with observed triplet quantum yields reaching as high as 156 ± 5%. Whereas previous studies have shown that the collision of a photoexcited chromophore with a ground-state chromophore can give rise to SF, here we demonstrate that the proximity and sufficient coupling through bond or space in pentacene dimers is enough to induce intramolecular SF where two triplets are generated on one molecule. PMID:25858954

  6. Photo-oxidation of histidine peptides yields high concentrations of unstable peroxides

    International Nuclear Information System (INIS)

    Policarpio, V.V.; Hawkins, C.L.; Davies, M.J.

    2003-01-01

    Oxidation of proteins by UV, and visible light in the presence of sensitizers, results in side chain modification as well as aggregation and fragmentation. In particular, singlet oxygen has been reported to oxidize Met, Trp, Tyr, Cys and His side chains in a selective manner. In this study the oxidation of histidine and its derivatives, and His-containing peptides is examined using a range of sensitizers, to determine whether peroxides are major intermediates, and the mechanism of formation of these species. Visible light-sensitised oxidation of Gly-His-Gly in the presence of oxygen and rose bengal gives unstable substrate-derived peroxides with the peroxide yield increasing with increasing photolysis time. Similar behaviour was detected with other photosensitizers, though the peroxide yields varied with the sensitizer at identical concentrations with rose bengal > aluminium phthalocyanine > hematoporphyrin IX > zinc phthalocyanine > tetrakisporphine. The peroxide yield was decreased in the presence of azide and enhanced when deuterium oxide was employed as the solvent, consistent with peroxide formation being singlet oxygen mediated. Experiments using anoxic conditions gave low yields of peroxides confirming the oxygen-dependence of these reactions. HPLC analysis showed rapid loss of the parent peptide, with subsequent formation of both stable and unstable products; these are currently being characterized by MS and NMR. Similar behavior has been observed with other His derivatives. The yield of singlet oxygen formed in these reactions has been estimated using a bleaching assay (N, N-dimethyl-4-nitrosoaniline). Quantification of singlet oxygen formation and Gly-His-Gly derived peroxide during rose bengal-mediated photooxidation indicated a conversion efficiency of the initial singlet oxygen into substrate-derived peroxides of ca. 75% indicating that peroxide formation is a highly efficient and major reaction pathway

  7. Effects of fulvic acid concentration and origin on photodegradation of polycyclic aromatic hydrocarbons in aqueous solution: Importance of active oxygen

    International Nuclear Information System (INIS)

    Xia Xinghui; Li Gongchen; Yang Zhifeng; Chen Yumin; Huang, Gordon H.

    2009-01-01

    With an Xe arc lamp house as simulated sunlight, the influences of fulvic acid (FA) concentration and origins on photodegradation of acenaphthene, fluorine, phenanthrene, fluoranthene and pyrene in aqueous solution have been studied. Similar effects of FAs, collected from five places around China, on polycyclic aromatic hydrocarbon (PAH) photodegradation have been observed. Active oxygen was of significance in PAH photodegradation with the presence of FAs. For systems with 1.25 mg L -1 FAs, the contributions of ·OH to PAH photodegradation rates were from 33% to 69%. FAs had two opposite effects, i.e., stimulating the generation of active oxygen and advancing PAH photodegradation; competing with PAHs for energy and photons and restraining PAH photodegradation. Generally, photodegradation rates of the 5 PAHs decreased with the increase of FAs concentration; except fluoranthene and pyrene were advanced in solutions with low FA concentration. The influences of FA concentration on PAH photodegradation were more significant than FA origin. - Influences of fulvic acid (FA) concentration on PAH photodegradation were more significant than FA origin, and active oxygen played an important role in PAH photodegradation

  8. Portable Cathode-Air-Vapor-Feed Electrochemical Medical Oxygen Concentrator, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Future space exploration missions present significant new challenges to crew health care capabilities, particularly in the efficient utilization of on-board oxygen...

  9. Removal method of fluorescent dyes as pretreatment for measurement of major ion concentrations and hydrogen and oxygen isotopic ratios

    International Nuclear Information System (INIS)

    Nakata, Kotaro; Hasegawa, Takuma; Kashiwaya, Koki; Kodama, Hiroki; Miyajima, Tohru

    2011-01-01

    The major ion concentration and isotope ratio of hydrogen and oxygen can provide important information for migration of groundwater. Sometimes, quantitative estimation of these chemical and isotopic characteristics of solution is necessary for groundwater containing fluorescent dyes, which are used in drilling borehole and tracer experiments. However, sometimes correct estimation is disturbed by dyes and they become a cause of troubles for measurement equipments. Thus development of method to remove dyes is required so that the characteristics of groundwater can be estimated without the negative effect of dyes on measurement or equipments. In this study, removal of four representative dyes (Uranin, Eosin, Naphthalenesulfonic acid sodium(NAP) and Amino G acid potassium salt (AG)) was investigated. Uranin and Eosin were found to be removed by non-ionic synthetic resin: HP2MG. 99.99% of the dyes were removed from initial solutions containing dyes with 10 mg/L after contact with resin, while the contact had little effect on ion concentrations and oxygen and hydrogen isotope ratios. Thus the chemical and isotopic characteristics of groundwater samples containing Uranin and Eosin can be obtained by using the HP2MG resin. On the other hand, the NAP and AG were found to be difficult to remove by the HP2MG resin but they were able to be removed by anion exchange resin (Dowex 1x8). Though contact of solution with Dowex 1x8 did not affect cation concentrations and hydrogen and oxygen isotope ratios, anion concentrations were changed by the contact. Therefore the Dowex 1x8 is only applicable to estimation of the cation concentrations and isotope ratio of hydrogen and oxygen. When both anion and cation concentrations from the samples were necessary, Uranin or Eosin were recommended as a tracer in drilling or tracer experiments. (author)

  10. High-spatial-resolution mapping of the oxygen concentration in cortical tissue (Conference Presentation)

    Science.gov (United States)

    Jaswal, Rajeshwer S.; Yaseen, Mohammad A.; Fu, Buyin; Boas, David A.; Sakadžic, Sava

    2016-03-01

    Due to a lack of imaging tools for high-resolution imaging of cortical tissue oxygenation, the detailed maps of the oxygen partial pressure (PO2) around arterioles, venules, and capillaries remain largely unknown. Therefore, we have limited knowledge about the mechanisms that secure sufficient oxygen delivery in microvascular domains during brain activation, and provide some metabolic reserve capacity in diseases that affect either microvascular networks or the regulation of cerebral blood flow (CBF). To address this challenge, we applied a Two-Photon PO2 Microscopy to map PO2 at different depths in mice cortices. Measurements were performed through the cranial window in the anesthetized healthy mice as well as in the mouse models of microvascular dysfunctions. In addition, microvascular morphology was recorded by the two-photon microscopy at the end of each experiment and subsequently segmented. Co-registration of the PO2 measurements and exact microvascular morphology enabled quantification of the tissue PO2 dependence on distance from the arterioles, capillaries, and venules at various depths. Our measurements reveal significant spatial heterogeneity of the cortical tissue PO2 distribution that is dominated by the high oxygenation in periarteriolar spaces. In cases of impaired oxygen delivery due to microvascular dysfunction, significant reduction in tissue oxygenation away from the arterioles was observed. These tissue domains may be the initial sites of cortical injury that can further exacerbate the progression of the disease.

  11. Impact of oxygen concentration on time to resolution of spontaneous pneumothorax in term infants: a population based cohort study

    Science.gov (United States)

    2014-01-01

    Background Little evidence exists regarding the optimal concentration of oxygen to use in the treatment of term neonates with spontaneous pneumothorax (SP). The practice of using high oxygen concentrations to promote “nitrogen washout” still exists at many centers. The aim of this study was to identify the time to clinical resolution of SP in term neonates treated with high oxygen concentrations (HO: FiO2 ≥ 60%), moderate oxygen concentrations (MO: FiO2 pneumothorax admitted to all neonatal intensive care units in Calgary, Alberta, Canada, within 72 hours of birth between 2006 and 2010. Newborns with congenital and chromosomal anomalies, meconium aspiration, respiratory distress syndrome, and transient tachypnea of newborn, pneumonia, tension pneumothorax requiring thoracocentesis or chest tube drainage or mechanical ventilation before the diagnosis of pneumothorax were excluded. The primary outcome was time to clinical resolution (hours) of SP. A Cox proportional hazards model was developed to assess differences in time to resolution of SP between treatment groups. Results Neonates were classified into three groups based on the treatment received: HO (n = 27), MO (n = 35) and RA (n = 30). There was no significant difference in time to resolution of SP between the three groups, median (range 25th-75th percentile) for HO = 12 hr (8–27), MO = 12 hr (5–24) and RA = 11 hr (4–24) (p = 0.50). A significant difference in time to resolution of SP was also not observed after adjusting for inhaled oxygen concentration [MO (a HR = 1.13, 95% CI 0.54-2.37); RA (a HR = 1.19, 95% CI 0.69-2.05)], gender (a HR = 0.87, 95% CI 0.53-1.43) and ACoRN respiratory score (a HR = 0.7, 95% CI 0.41-1.34). Conclusions Supplemental oxygen use or nitrogen washout was not associated with faster resolution of SP. Infants treated with room air remained stable and did not require supplemental oxygen at any point of their admission. PMID

  12. Effects of bottom water oxygen concentrations on mercury distribution and speciation in sediments below the oxygen minimum zone of the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, P.; Mason, R.P.; Jayachandran, S.; Vudamala, K.; Armoury, K.; Sarkar, Arindam; Chakraborty, S.; Bardhan, P.; Naik, R.

    benthic flux of MeHg to the overlying water (Hollweg et al., 2010; Balcom et al., 2008). On the contrary, however, a study in the Gulf of Mexico did not find that MeHg in bottom waters correlated with the extent of hypoxia (Liu et al., 2015... in the sediments of the so-called “dead zone” in the Gulf of Mexico. Others (Mason et al., 2006; Emili et al., 2011) have shown that total Hg and MeHg fluxes from sediments are enhanced by low oxygen concentrations in the overlying waters. The aim of this study...

  13. An in silico analysis of oxygen uptake of a mild COPD patient during rest and exercise using a portable oxygen concentrator

    Directory of Open Access Journals (Sweden)

    Katz I

    2016-09-01

    Full Text Available Ira Katz,1,2 Marine Pichelin,1 Spyridon Montesantos,1 Min-Yeong Kang,3 Bernard Sapoval,3,4 Kaixian Zhu,5 Charles-Philippe Thevenin,5 Robert McCoy,6 Andrew R Martin,7 Georges Caillibotte1 1Medical R&D, Air Liquide Santé International, Centre de Recherche Paris-Saclay, Les Loges-en-Josas, France; 2Department of Mechanical Engineering, Lafayette College, Easton, PA, USA; 3Physique de la Matière Condensée, CNRS, Ecole Polytechnique, Palaiseau, 4Centre de Mathématiques et de leurs Applications, CNRS, UniverSud, Cachan, 5Centre Explor!, Air Liquide Healthcare, Gentilly, France; 6Valley Inspired Products, Inc, Apple Valley, MN, USA; 7Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada Abstract: Oxygen treatment based on intermittent-flow devices with pulse delivery modes available from portable oxygen concentrators (POCs depends on the characteristics of the delivered pulse such as volume, pulse width (the time of the pulse to be delivered, and pulse delay (the time for the pulse to be initiated from the start of inhalation as well as a patient’s breathing characteristics, disease state, and respiratory morphology. This article presents a physiological-based analysis of the performance, in terms of blood oxygenation, of a commercial POC at different settings using an in silico model of a COPD patient at rest and during exercise. The analysis encompasses experimental measurements of pulse volume, width, and time delay of the POC at three different settings and two breathing rates related to rest and exercise. These experimental data of device performance are inputs to a physiological-based model of oxygen uptake that takes into account the real dynamic nature of gas exchange to illustrate how device- and patient-specific factors can affect patient oxygenation. This type of physiological analysis that considers the true effectiveness of oxygen transfer to the blood, as opposed to delivery to the nose (or mouth, can be

  14. Spin nematics next to spin singlets

    Science.gov (United States)

    Yokoyama, Yuto; Hotta, Chisa

    2018-05-01

    We provide a route to generate nematic order in a spin-1/2 system. Unlike the well-known magnon-binding mechanism, our spin nematics requires neither the frustration effect nor spin polarization in a high field or in the vicinity of a ferromagnet, but instead appears next to the spin singlet phase. We start from a state consisting of a quantum spin-1/2 singlet dimer placed on each site of a triangular lattice, and show that interdimer ring exchange interactions efficiently dope the SU(2) triplets that itinerate and interact, easily driving a stable singlet state to either Bose-Einstein condensates or a triplet crystal, some hosting a spin nematic order. A variety of roles the ring exchange serves includes the generation of a bilinear-biquadratic interaction between nearby triplets, which is responsible for the emergent nematic order separated from the singlet phase by a first-order transition.

  15. Signatures for exotic quark singlets from superstrings

    International Nuclear Information System (INIS)

    Barger, V.; Deshpande, N.G.; Gunion, J.F.

    1986-09-01

    We consider various scenarios, at Superconducting Super Collider energy and luminosity, for detection of the extra colored, weak isospin singlet, charge -1/3 heavy fermion resulting from E 6 compactification in superstring theories

  16. Estimate of oxygen consumption and intracellular zinc concentration of human spermatozoa in relation to motility.

    Science.gov (United States)

    Henkel, Ralf R; Defosse, Kerstin; Koyro, Hans-Wilhelm; Weissmann, Norbert; Schill, Wolf-Bernhard

    2003-03-01

    To investigate the human sperm oxygen/energy consumption and zinc content in relation to motility. In washed spermatozoa from 67 ejaculates, the oxygen consumption was determined. Following calculation of the total oxygen consumed by the Ideal Gas Law, the energy consumption of spermatozoa was calculated. In addition, the zinc content of the sperm was determined using an atomic absorption spectrometer. The resulting data were correlated to the vitality and motility. The oxygen consumption averaged 0.24 micromol/10(6) sperm x 24h, 0.28 micromol/10(6) live sperm x 24h and 0.85 micromol/10(6) live motile sperm x 24h. Further calculations revealed that sperm motility was the most energy consuming process (164.31 mJ/10(6) motile spermatozoa x 24h), while the oxygen consumption of the total spermatozoa was 46.06 mJ/10(6) spermatozoa x 24h. The correlation of the oxygen/energy consumption and zinc content with motility showed significant negative correlations (r= -0.759; P<0.0001 and r=-0.441; P<0.0001, respectively). However, when correlating sperm energy consumption with the zinc content, a significant positive relation (r=0.323; P=0.01) was observed. Poorly motile sperm are actually wasting the available energy. Moreover, our data clearly support the "Geometric Clutch Model" of the axoneme function and demonstrate the importance of the outer dense fibers for the generation of sperm motility, especially progressive motility.

  17. Singlet fermionic dark matter with Veltman conditions

    OpenAIRE

    Kim, Yeong Gyun; Lee, Kang Young; Nam, Soo-hyeon

    2018-01-01

    We reexamine a renormalizable model of a fermionic dark matter with a gauge singlet Dirac fermion and a real singlet scalar which can ameliorate the scalar mass hierarchy problem of the Standard Model (SM). Our model setup is the minimal extension of the SM for which a realistic dark matter (DM) candidate is provided and the cancellation of one-loop quadratic divergence to the scalar masses can be achieved by the Veltman condition (VC) simultaneously. This model extension, although renormaliz...

  18. Singlet axial constant from QCD sum rules

    International Nuclear Information System (INIS)

    Belitskij, A.V.; Teryaev, O.V.

    1995-01-01

    We analyze the singlet axial form factor of the proton for small momentum transferred in the framework of QCD sum rules using the interpolating nucleon current which explicitly accounts for the gluonic degrees of freedom. As the result we come to the quantitative prediction of the singlet axial constant. It is shown that the bilocal power corrections play the most important role in the analysis. 21 refs., 3 figs

  19. In situ quantification of ultra-low O2 concentrations in oxygen minimum zones

    DEFF Research Database (Denmark)

    Larsen, Morten; Lehner, Philipp; Borisov, Sergey M.

    2016-01-01

    based on the palladium(II)-benzoporphyrin luminophore, immobilized in a perfluorinated matrix with high O2 permeability. The trace sensor has a detection limit of ∼5 nmol L−1 with a dynamic range extending up to ∼2 μmol L−1. The sensor demonstrates a response time ..., and fully reversible response to hydrostatic pressure and temperature. The sensor showed excellent stability for continuously measurements during depth profiling in Oxygen Minimum Zones (OMZ). The novel sensor was deployed in situ using a Trace Oxygen Profiler instrument (TOP) equipped with two additional O...

  20. Local Cytokine Concentrations and Oxygen Pressure Are Related to Maturation of the Collateral Circulation in Humans

    NARCIS (Netherlands)

    Schirmer, Stephan H.; van Royen, Niels; Moerland, Perry D.; Fledderus, Joost O.; Henriques, José P.; van der Schaaf, René J.; Vis, Marije M.; Baan, Jan; Koch, Karel T.; Horrevoets, Anton J. G.; Hoefer, Imo E.; Piek, Jan J.

    2009-01-01

    Objectives Our aim was to determine cytokine and oxygen gradients over the collateral circulation in humans. Background The molecular background of the maturation of the collateral circulation in response to coronary narrowing is poorly understood in humans, partly because of difficulties in

  1. Experiments on how photo- and background ionization affect positive streamers: oxygen concentration, repetition and radioactivity

    NARCIS (Netherlands)

    Nijdam, S.; Veldhuizen, van E.M.; Ebert, U.

    2011-01-01

    Positive streamers in air and other oxygen-nitrogen mixtures are generally believed to propagate against the electron drift direction due to photo-ionization. Photo-ionization is the non-local ionization of O2-molecules by UV radiation from excited N2-molecules. This facilitates the streamer

  2. 14 CFR Special Federal Aviation... - Rules for use of portable oxygen concentrator systems on board aircraft

    Science.gov (United States)

    2010-01-01

    ... products and is in good condition free from damage or other signs of excessive wear or abuse; (3) The user... planned flight. The user must carry on the flight a sufficient number of batteries to power the device for... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Rules for use of portable oxygen...

  3. Deep vs shallow nature of oxygen vacancies and consequent n -type carrier concentrations in transparent conducting oxides

    Science.gov (United States)

    Buckeridge, J.; Catlow, C. R. A.; Farrow, M. R.; Logsdail, A. J.; Scanlon, D. O.; Keal, T. W.; Sherwood, P.; Woodley, S. M.; Sokol, A. A.; Walsh, A.

    2018-05-01

    The source of n -type conductivity in undoped transparent conducting oxides has been a topic of debate for several decades. The point defect of most interest in this respect is the oxygen vacancy, but there are many conflicting reports on the shallow versus deep nature of its related electronic states. Here, using a hybrid quantum mechanical/molecular mechanical embedded cluster approach, we have computed formation and ionization energies of oxygen vacancies in three representative transparent conducting oxides: In2O3 ,SnO2, and ZnO. We find that, in all three systems, oxygen vacancies form well-localized, compact donors. We demonstrate, however, that such compactness does not preclude the possibility of these states being shallow in nature, by considering the energetic balance between the vacancy binding electrons that are in localized orbitals or in effective-mass-like diffuse orbitals. Our results show that, thermodynamically, oxygen vacancies in bulk In2O3 introduce states above the conduction band minimum that contribute significantly to the observed conductivity properties of undoped samples. For ZnO and SnO2, the states are deep, and our calculated ionization energies agree well with thermochemical and optical experiments. Our computed equilibrium defect and carrier concentrations, however, demonstrate that these deep states may nevertheless lead to significant intrinsic n -type conductivity under reducing conditions at elevated temperatures. Our study indicates the importance of oxygen vacancies in relation to intrinsic carrier concentrations not only in In2O3 , but also in SnO2 and ZnO.

  4. BaSi2 formation mechanism in thermally evaporated films and its application to reducing oxygen impurity concentration

    Science.gov (United States)

    Hara, Kosuke O.; Yamamoto, Chiaya; Yamanaka, Junji; Arimoto, Keisuke; Nakagawa, Kiyokazu; Usami, Noritaka

    2018-04-01

    Thermal evaporation is a simple and rapid method to fabricate semiconducting BaSi2 films. In this study, to elucidate the BaSi2 formation mechanism, the microstructure of a BaSi2 epitaxial film fabricated by thermal evaporation has been investigated by transmission electron microscopy. The BaSi2 film is found to consist of three layers with different microstructural characteristics, which is well explained by assuming two stages of film deposition. In the first stage, BaSi2 forms through the diffusion of Ba atoms from the deposited Ba-rich film to the Si substrate while in the second stage, the mutual diffusion of Ba and Si atoms in the film leads to BaSi2 formation. On the basis of the BaSi2 formation mechanism, two issues are addressed. One is the as-yet unclarified reason for epitaxial growth. It is found important to quickly form BaSi2 in the first stage for the epitaxial growth of upper layers. The other issue is the high oxygen concentration in BaSi2 films around the BaSi2-Si interface. Two routes of oxygen incorporation, i.e., oxidation of the Si substrate surface and initially deposited Ba-rich layer by the residual gas, are identified. On the basis of this knowledge, oxygen concentration is decreased by reducing the holding time of the substrate at high temperatures and by premelting of the source. In addition, X-ray diffraction results show that the decrease in oxygen concentration can lead to an increased proportion of a-axis-oriented grains.

  5. Effect of oxygen concentration on human embryo development evaluated by time-lapse monitoring

    DEFF Research Database (Denmark)

    Ingerslev, Hans Jakob; Hindkjær, Johnny Juhl; Kirkegaard, Kirstine

    2012-01-01

    -points for each cell division and blastocyst stages were registered until 120 hours after oocyte retrieval. Only 2PN embryos completing the first cleavage were evaluated. The groups were compared using one-way ANOVA or Kruskall-Wallis test. Estimates are reported as medians with 95% confidence intervals. Time......Introduction: Data from a number of studies indicate -but not unequivocally- that culture of embryos in 5% O2 compared to 20% O2 improves blastocyst formation in humans and various animal species and may yield better pregnancy rates in IVF. The detrimental effects of atmospheric oxygen were...... was to evaluate the influence of oxygen tension on human pre-implantation development using time-lapse monitoring. Materials and methods: Human embryos were cultured to the blastocyst stage in a time-lapse incubator (EmbryoScope™) in 20% O2 (group 1), 20% O2 for 24 hours followed by culture in 5% O2 (group 2...

  6. CLIMATE CHANGE. Long-term climate forcing by atmospheric oxygen concentrations.

    Science.gov (United States)

    Poulsen, Christopher J; Tabor, Clay; White, Joseph D

    2015-06-12

    The percentage of oxygen in Earth's atmosphere varied between 10% and 35% throughout the Phanerozoic. These changes have been linked to the evolution, radiation, and size of animals but have not been considered to affect climate. We conducted simulations showing that modulation of the partial pressure of oxygen (pO2), as a result of its contribution to atmospheric mass and density, influences the optical depth of the atmosphere. Under low pO2 and a reduced-density atmosphere, shortwave scattering by air molecules and clouds is less frequent, leading to a substantial increase in surface shortwave forcing. Through feedbacks involving latent heat fluxes to the atmosphere and marine stratus clouds, surface shortwave forcing drives increases in atmospheric water vapor and global precipitation, enhances greenhouse forcing, and raises global surface temperature. Our results implicate pO2 as an important factor in climate forcing throughout geologic time. Copyright © 2015, American Association for the Advancement of Science.

  7. Aberrant patterns of X chromosome inactivation in a new line of human embryonic stem cells established in physiological oxygen concentrations.

    Science.gov (United States)

    de Oliveira Georges, Juliana Andrea; Vergani, Naja; Fonseca, Simone Aparecida Siqueira; Fraga, Ana Maria; de Mello, Joana Carvalho Moreira; Albuquerque, Maria Cecília R Maciel; Fujihara, Litsuko Shimabukuro; Pereira, Lygia Veiga

    2014-08-01

    One of the differences between murine and human embryonic stem cells (ESCs) is the epigenetic state of the X chromosomes in female lines. Murine ESCs (mESCs) present two transcriptionally active Xs that will undergo the dosage compensation process of XCI upon differentiation, whereas most human ESCs (hESCs) spontaneously inactivate one X while keeping their pluripotency. Whether this reflects differences in embryonic development of mice and humans, or distinct culture requirements for the two kinds of pluripotent cells is not known. Recently it has been shown that hESCs established in physiological oxygen levels are in a stable pre-XCI state equivalent to that of mESCs, suggesting that culture in low oxygen concentration is enough to preserve that epigenetic state of the X chromosomes. Here we describe the establishment of two new lines of hESCs under physiological oxygen level and the characterization of the XCI state in the 46,XX line BR-5. We show that a fraction of undifferentiated cells present XIST RNA accumulation and single H3K27me foci, characteristic of the inactive X. Moreover, analysis of allele specific gene expression suggests that pluripotent BR-5 cells present completely skewed XCI. Our data indicate that physiological levels of oxygen are not sufficient for the stabilization of the pre-XCI state in hESCs.

  8. Quantitative spatially resolved measurement of tissue chromophore concentrations using photoacoustic spectroscopy: application to the measurement of blood oxygenation and haemoglobin concentration

    Science.gov (United States)

    Laufer, Jan; Delpy, Dave; Elwell, Clare; Beard, Paul

    2007-01-01

    A new approach based on pulsed photoacoustic spectroscopy for non-invasively quantifying tissue chromophore concentrations with high spatial resolution has been developed. The technique is applicable to the quantification of tissue chromophores such as oxyhaemoglobin (HbO2) and deoxyhaemoglobin (HHb) for the measurement of physiological parameters such as blood oxygen saturation (SO2) and total haemoglobin concentration. It can also be used to quantify the local accumulation of targeted contrast agents used in photoacoustic molecular imaging. The technique employs a model-based inversion scheme to recover the chromophore concentrations from photoacoustic measurements. This comprises a numerical forward model of the detected time-dependent photoacoustic signal that incorporates a multiwavelength diffusion-based finite element light propagation model to describe the light transport and a time-domain acoustic model to describe the generation, propagation and detection of the photoacoustic wave. The forward model is then inverted by iteratively fitting it to measurements of photoacoustic signals acquired at different wavelengths to recover the chromophore concentrations. To validate this approach, photoacoustic signals were generated in a tissue phantom using nanosecond laser pulses between 740 nm and 1040 nm. The tissue phantom comprised a suspension of intralipid, blood and a near-infrared dye in which three tubes were immersed. Blood at physiological haemoglobin concentrations and oxygen saturation levels ranging from 2% to 100% was circulated through the tubes. The signal amplitude from different temporal sections of the detected photoacoustic waveforms was plotted as a function of wavelength and the forward model fitted to these data to recover the concentrations of HbO2 and HHb, total haemoglobin concentration and SO2. The performance was found to compare favourably to that of a laboratory CO-oximeter with measurement resolutions of ±3.8 g l-1 (±58 µM) and ±4

  9. Quantitative spatially resolved measurement of tissue chromophore concentrations using photoacoustic spectroscopy: application to the measurement of blood oxygenation and haemoglobin concentration

    Energy Technology Data Exchange (ETDEWEB)

    Laufer, Jan; Delpy, Dave; Elwell, Clare; Beard, Paul [Department of Medical Physics and Bioengineering, University College London, Malet Place Engineering Building, London WC1E 6BT (United Kingdom)

    2007-01-07

    A new approach based on pulsed photoacoustic spectroscopy for non-invasively quantifying tissue chromophore concentrations with high spatial resolution has been developed. The technique is applicable to the quantification of tissue chromophores such as oxyhaemoglobin (HbO{sub 2}) and deoxyhaemoglobin (HHb) for the measurement of physiological parameters such as blood oxygen saturation (SO{sub 2}) and total haemoglobin concentration. It can also be used to quantify the local accumulation of targeted contrast agents used in photoacoustic molecular imaging. The technique employs a model-based inversion scheme to recover the chromophore concentrations from photoacoustic measurements. This comprises a numerical forward model of the detected time-dependent photoacoustic signal that incorporates a multiwavelength diffusion-based finite element light propagation model to describe the light transport and a time-domain acoustic model to describe the generation, propagation and detection of the photoacoustic wave. The forward model is then inverted by iteratively fitting it to measurements of photoacoustic signals acquired at different wavelengths to recover the chromophore concentrations. To validate this approach, photoacoustic signals were generated in a tissue phantom using nanosecond laser pulses between 740 nm and 1040 nm. The tissue phantom comprised a suspension of intralipid, blood and a near-infrared dye in which three tubes were immersed. Blood at physiological haemoglobin concentrations and oxygen saturation levels ranging from 2% to 100% was circulated through the tubes. The signal amplitude from different temporal sections of the detected photoacoustic waveforms was plotted as a function of wavelength and the forward model fitted to these data to recover the concentrations of HbO{sub 2} and HHb, total haemoglobin concentration and SO{sub 2}. The performance was found to compare favourably to that of a laboratory CO-oximeter with measurement resolutions of {+-}3

  10. Quantitative spatially resolved measurement of tissue chromophore concentrations using photoacoustic spectroscopy: application to the measurement of blood oxygenation and haemoglobin concentration

    International Nuclear Information System (INIS)

    Laufer, Jan; Delpy, Dave; Elwell, Clare; Beard, Paul

    2007-01-01

    A new approach based on pulsed photoacoustic spectroscopy for non-invasively quantifying tissue chromophore concentrations with high spatial resolution has been developed. The technique is applicable to the quantification of tissue chromophores such as oxyhaemoglobin (HbO 2 ) and deoxyhaemoglobin (HHb) for the measurement of physiological parameters such as blood oxygen saturation (SO 2 ) and total haemoglobin concentration. It can also be used to quantify the local accumulation of targeted contrast agents used in photoacoustic molecular imaging. The technique employs a model-based inversion scheme to recover the chromophore concentrations from photoacoustic measurements. This comprises a numerical forward model of the detected time-dependent photoacoustic signal that incorporates a multiwavelength diffusion-based finite element light propagation model to describe the light transport and a time-domain acoustic model to describe the generation, propagation and detection of the photoacoustic wave. The forward model is then inverted by iteratively fitting it to measurements of photoacoustic signals acquired at different wavelengths to recover the chromophore concentrations. To validate this approach, photoacoustic signals were generated in a tissue phantom using nanosecond laser pulses between 740 nm and 1040 nm. The tissue phantom comprised a suspension of intralipid, blood and a near-infrared dye in which three tubes were immersed. Blood at physiological haemoglobin concentrations and oxygen saturation levels ranging from 2% to 100% was circulated through the tubes. The signal amplitude from different temporal sections of the detected photoacoustic waveforms was plotted as a function of wavelength and the forward model fitted to these data to recover the concentrations of HbO 2 and HHb, total haemoglobin concentration and SO 2 . The performance was found to compare favourably to that of a laboratory CO-oximeter with measurement resolutions of ±3.8 g l -1 (±58

  11. Growth of the obligate anaerobe Desulfovibrio vulgaris Hildenborough under continuous low oxygen concentration sparging: impact of the membrane-bound oxygen reductases.

    Science.gov (United States)

    Ramel, Fanny; Brasseur, Gael; Pieulle, Laetitia; Valette, Odile; Hirschler-Réa, Agnès; Fardeau, Marie Laure; Dolla, Alain

    2015-01-01

    Although obligate anaerobe, the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough (DvH) exhibits high aerotolerance that involves several enzymatic systems, including two membrane-bound oxygen reductases, a bd-quinol oxidase and a cc(b/o)o3 cytochrome oxidase. Effect of constant low oxygen concentration on growth and morphology of the wild-type, single (Δbd, Δcox) and double deletion (Δcoxbd) mutant strains of the genes encoding these oxygen reductases was studied. When both wild-type and deletion mutant strains were cultured in lactate/sulfate medium under constant 0.02% O2 sparging, they were able to grow but the final biomasses and the growth yield were lower than that obtained under anaerobic conditions. At the end of the growth, lactate was not completely consumed and when conditions were then switched to anaerobic, growth resumed. Time-lapse microscopy revealed that a large majority of the cells were then able to divide (over 97%) but the time to recover a complete division event was longer for single deletion mutant Δbd than for the three other strains. Determination of the molar growth yields on lactate suggested that a part of the energy gained from lactate oxidation was derived toward cells protection/repairing against oxidative conditions rather than biosynthesis, and that this part was higher in the single deletion mutant Δbd and, to a lesser extent, Δcox strains. Our data show that when DvH encounters oxidative conditions, it is able to stop growing and to rapidly resume growing when conditions are switched to anaerobic, suggesting that it enters active dormancy sate under oxidative conditions. We propose that the pyruvate-ferredoxin oxidoreductase (PFOR) plays a central role in this phenomenon by reversibly switching from an oxidative-sensitive fully active state to an oxidative-insensitive inactive state. The oxygen reductases, and especially the bd-quinol oxidase, would have a crucial function by maintaining reducing conditions

  12. Growth of the obligate anaerobe Desulfovibrio vulgaris Hildenborough under continuous low oxygen concentration sparging: impact of the membrane-bound oxygen reductases.

    Directory of Open Access Journals (Sweden)

    Fanny Ramel

    Full Text Available Although obligate anaerobe, the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough (DvH exhibits high aerotolerance that involves several enzymatic systems, including two membrane-bound oxygen reductases, a bd-quinol oxidase and a cc(b/oo3 cytochrome oxidase. Effect of constant low oxygen concentration on growth and morphology of the wild-type, single (Δbd, Δcox and double deletion (Δcoxbd mutant strains of the genes encoding these oxygen reductases was studied. When both wild-type and deletion mutant strains were cultured in lactate/sulfate medium under constant 0.02% O2 sparging, they were able to grow but the final biomasses and the growth yield were lower than that obtained under anaerobic conditions. At the end of the growth, lactate was not completely consumed and when conditions were then switched to anaerobic, growth resumed. Time-lapse microscopy revealed that a large majority of the cells were then able to divide (over 97% but the time to recover a complete division event was longer for single deletion mutant Δbd than for the three other strains. Determination of the molar growth yields on lactate suggested that a part of the energy gained from lactate oxidation was derived toward cells protection/repairing against oxidative conditions rather than biosynthesis, and that this part was higher in the single deletion mutant Δbd and, to a lesser extent, Δcox strains. Our data show that when DvH encounters oxidative conditions, it is able to stop growing and to rapidly resume growing when conditions are switched to anaerobic, suggesting that it enters active dormancy sate under oxidative conditions. We propose that the pyruvate-ferredoxin oxidoreductase (PFOR plays a central role in this phenomenon by reversibly switching from an oxidative-sensitive fully active state to an oxidative-insensitive inactive state. The oxygen reductases, and especially the bd-quinol oxidase, would have a crucial function by maintaining

  13. Adsorption/desorption of low concentration of carbonyl sulfide by impregnated activated carbon under micro-oxygen conditions

    International Nuclear Information System (INIS)

    Wang, Xueqian; Qiu, Juan; Ning, Ping; Ren, Xiaoguang; Li, Ziyan; Yin, Zaifei; Chen, Wei; Liu, Wei

    2012-01-01

    Highlights: ► Carbonyl sulfide can be catalytic oxidized by micro-oxygen in the off-gas. ► How to use the trace oxygen for the oxidation of carbonyl sulfide was a challenge. ► The SO 4 2− species in the adsorbent sample were generated by a catalytic oxidation process. - Abstract: Activated carbon modified with different impregnants has been studied for COS removal efficiency under micro-oxygen conditions. Activated carbon modified with Cu(NO 3 ) 2 –CoPcS–KOH (denoted as Cu–Co–KW) is found to have markedly enhanced adsorption purification ability. In the adsorption purification process, the reaction temperature, oxygen concentration, and relative humidity of the gas are determined to be three crucial factors. A breakthrough of 43.34 mg COS/g adsorbent at 60 °S and 30% relative humidity with 1.0% oxygen is shown in Cu–Co–KW for removing COS. The structures of the activated carbon samples are characterized using nitrogen adsorption, and their surface chemical structures are analyzed with X-ray photoelectron spectroscopy (XPS). Modification of Cu(NO 3 ) 2 –CoPcS–KOH appears to improve the COS removal capacity significantly, during which, SO 4 2− is presumably formed, strongly adsorbed, and present in the micropores ranging from 0.7 to 1.5 nm. TPD is used to identify the products containing sulfur species on the carbon surface, where SO 2 and COS are detected in the effluent gas generated from exhausted Cu–Co–KW (denoted Cu–Co–KWE). According to the current study results, the activated carbon impregnated with Cu(NO 3 ) 2 –CoPcS–KOH promises a good candidate for COS adsorbent, with the purified gas meeting requirements for desirable chemical feed stocks.

  14. Adsorption/desorption of low concentration of carbonyl sulfide by impregnated activated carbon under micro-oxygen conditions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xueqian, E-mail: wxqian3000@yahoo.com.cn [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Qiu, Juan; Ning, Ping; Ren, Xiaoguang; Li, Ziyan; Yin, Zaifei; Chen, Wei; Liu, Wei [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

    2012-08-30

    Highlights: Black-Right-Pointing-Pointer Carbonyl sulfide can be catalytic oxidized by micro-oxygen in the off-gas. Black-Right-Pointing-Pointer How to use the trace oxygen for the oxidation of carbonyl sulfide was a challenge. Black-Right-Pointing-Pointer The SO{sub 4}{sup 2-} species in the adsorbent sample were generated by a catalytic oxidation process. - Abstract: Activated carbon modified with different impregnants has been studied for COS removal efficiency under micro-oxygen conditions. Activated carbon modified with Cu(NO{sub 3}){sub 2}-CoPcS-KOH (denoted as Cu-Co-KW) is found to have markedly enhanced adsorption purification ability. In the adsorption purification process, the reaction temperature, oxygen concentration, and relative humidity of the gas are determined to be three crucial factors. A breakthrough of 43.34 mg COS/g adsorbent at 60 Degree-Sign S and 30% relative humidity with 1.0% oxygen is shown in Cu-Co-KW for removing COS. The structures of the activated carbon samples are characterized using nitrogen adsorption, and their surface chemical structures are analyzed with X-ray photoelectron spectroscopy (XPS). Modification of Cu(NO{sub 3}){sub 2}-CoPcS-KOH appears to improve the COS removal capacity significantly, during which, SO{sub 4}{sup 2-} is presumably formed, strongly adsorbed, and present in the micropores ranging from 0.7 to 1.5 nm. TPD is used to identify the products containing sulfur species on the carbon surface, where SO{sub 2} and COS are detected in the effluent gas generated from exhausted Cu-Co-KW (denoted Cu-Co-KWE). According to the current study results, the activated carbon impregnated with Cu(NO{sub 3}){sub 2}-CoPcS-KOH promises a good candidate for COS adsorbent, with the purified gas meeting requirements for desirable chemical feed stocks.

  15. Oxygen 18 isotopic analysis of sub-glacial concentrations of the Laurentide Ice Sheet

    Energy Technology Data Exchange (ETDEWEB)

    Hillaire-Marcel, C [Quebec Univ., Montreal (Canada); Cailleux, A [Observatoire de Paris, Section de Meudon, 92 (France); Soucy, J

    1979-07-01

    Calcareous concretions occuring on Grenvillian gneiss have been discovered north of Hull, Quebec. Their structure and isotopic composition (delta/sub PDB//sup 18/O approximately equal to -26%; delta/sub PDB//sup 13/C approximately equal to 0%; /sup 14/C age > 35,000 BP) indicate subglacial conditions of precipitation. It is concluded that they were deposited at the base of the Laurentide ice sheet. Assuming equilibrium conditions with the subglacial film of water during precipitation of calcite, it is possible to define a -27.5 to -31.8% (vs. 'standard mean ocean water' (SMOW)) range for the oxygen-18 content of ice.

  16. Oxygen discharge and post-discharge kinetics experiments and modeling for the electric oxygen-iodine laser system.

    Science.gov (United States)

    Palla, A D; Zimmerman, J W; Woodard, B S; Carroll, D L; Verdeyen, J T; Lim, T C; Solomon, W C

    2007-07-26

    Laser oscillation at 1315 nm on the I(2P1/2)-->I(2P3/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O2(a1Delta) produced using a low-pressure oxygen/helium/nitric oxide discharge. In the electric discharge oxygen-iodine laser (ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds levels of complexity to the singlet oxygen generator (SOG) kinetics which are not encountered in a classic purely chemical O2(a1Delta) generation system. The advanced model BLAZE-IV has been introduced to study the energy-transfer laser system dynamics and kinetics. Levels of singlet oxygen, oxygen atoms, and ozone are measured experimentally and compared with calculations. The new BLAZE-IV model is in reasonable agreement with O3, O atom, and gas temperature measurements but is under-predicting the increase in O2(a1Delta) concentration resulting from the presence of NO in the discharge and under-predicting the O2(b1Sigma) concentrations. A key conclusion is that the removal of oxygen atoms by NOX species leads to a significant increase in O2(a1Delta) concentrations downstream of the discharge in part via a recycling process; however, there are still some important processes related to the NOX discharge kinetics that are missing from the present modeling. Further, the removal of oxygen atoms dramatically inhibits the production of ozone in the downstream kinetics.

  17. Direct measurement of local oxygen concentration in the bone marrow of live animals

    Science.gov (United States)

    Spencer, Joel A.; Ferraro, Francesca; Roussakis, Emmanuel; Klein, Alyssa; Wu, Juwell; Runnels, Judith M.; Zaher, Walid; Mortensen, Luke J.; Alt, Clemens; Turcotte, Raphaël; Yusuf, Rushdia; Côté, Daniel; Vinogradov, Sergei A.; Scadden, David T.; Lin, Charles P.

    2014-04-01

    Characterization of how the microenvironment, or niche, regulates stem cell activity is central to understanding stem cell biology and to developing strategies for the therapeutic manipulation of stem cells. Low oxygen tension (hypoxia) is commonly thought to be a shared niche characteristic in maintaining quiescence in multiple stem cell types. However, support for the existence of a hypoxic niche has largely come from indirect evidence such as proteomic analysis, expression of hypoxia inducible factor-1α (Hif-1α) and related genes, and staining with surrogate hypoxic markers (for example, pimonidazole). Here we perform direct in vivo measurements of local oxygen tension (pO2) in the bone marrow of live mice. Using two-photon phosphorescence lifetime microscopy, we determined the absolute pO2 of the bone marrow to be quite low (hypoxic as it is perfused with small arteries that are often positive for the marker nestin. These pO2 values change markedly after radiation and chemotherapy, pointing to the role of stress in altering the stem cell metabolic microenvironment.

  18. Optical noninvasive calculation of hemoglobin components concentrations and fractional oxygen saturation using a ring-scattering pulse oximeter

    Science.gov (United States)

    Abdallah, Omar; Stork, Wilhelm; Muller-Glaser, Klaus

    2004-06-01

    The deficiencies of the currently used pulse oximeter are discussed in diverse literature. A hazardous pitfalls of this method is that the pulse oximeter will not detect carboxyhemoglobin (COHb) and methemoglobin (metHb) concentrations. This leads to incorrect measurement of oxygen saturation by carbon monoxide poisoning and methemoglobinemia. Also the total hemoglobin concentration will not be considered and can only be measured in-vitro up to now. A second pitfall of the standard pulse oximetry is that it will not be able to show a result by low perfusion of tissues. This case is available inter alia when the patient is under shock or has a low blood pressure. The new non-invasive system we designed measures the actual (fractional) oxygen saturation and hemoglobin concentration. It will enable us also to measure COHb and metHb. The measurement can be applied at better perfused body central parts. Four or more light emitting diodes (LEDs) or laser diodes (LDs) and five photodiodes (PDs) are used. The reflected light signal detected by photodiodes is processed using a modified Lambert-Beer law (I=I0×e-α.d ). According to this law, when a non scattering probe is irradiated with light having the incident intensity I0, the intensity of transmitted light I decays exponentially with the absorption coefficient a of that probe and its thickness d. Modifications of this law have been performed following the theoretical developed models in literature, Monte Carlo simulation and experimental measurement.

  19. Oxygen 18 concentration profile measurements near the surface by 18O(p,α)15N resonance reaction

    International Nuclear Information System (INIS)

    Amsel, G.; David, D.

    1975-01-01

    The method of spectrum reduction in nuclear reaction microanalysis does not allow to obtain depth resolutions better than the order of 2000A. Resolutions of the order of 200A may be obtained by using the narrow resonance technique, when applied to thin films. The latter technique was extended to thick targets, with deep concentration profiles presenting a sharp gradient near the surface. This method is presented and illustrated by the study of 18 O profiles in oxygen diffusion measurements in growing ZrO 2 , using the 629keV resonance of the reaction 18 O(p,α) 15 N [fr

  20. Oxygen concentration cell for the measurements of the standard molar Gibbs energy of formation of Nd6UO12(s)

    International Nuclear Information System (INIS)

    Sahu, Manjulata; Dash, Smruti

    2011-01-01

    The standard molar Gibbs energies of formation of Nd 6 UO 12 (s) have been measured using an oxygen concentration cell with yttria stabilized zirconia as solid electrolyte. Δ f G m o (T) for Nd 6 UO 12 (s) has been calculated using the measured and required thermodynamic data from the literature. The calculated Gibbs energy expression can be given as: Δ f G m o (Nd 6 UO 12 , s,T)/(± 2.3) kJmol -1 = -6660.1+1.0898 (T/K). (author)

  1. The influence of oxygen concentration on the combustion of a fuel/oxidizer mixture

    Energy Technology Data Exchange (ETDEWEB)

    Biteau, H. [School of Engineering and Electronics, BRE Centre for Fire Safety Engineering, The University of Edinburgh, Edinburgh EH9 3JL (United Kingdom); Institut National de l' Environnement Industriel et des Risques, Parc Technologique Alata, Verneuil en Halatte (France); Fuentes, A. [Institut Universitaire des Systemes Thermiques Industriels (CNRS UMR 6595), Universite de Provence, 13453 Marseille Cedex 13 (France); Marlair, G. [Institut National de l' Environnement Industriel et des Risques, Parc Technologique Alata, Verneuil en Halatte (France); Torero, J.L. [School of Engineering and Electronics, BRE Centre for Fire Safety Engineering, The University of Edinburgh, Edinburgh EH9 3JL (United Kingdom)

    2010-04-15

    The aim of the present study is to investigate the influence of the O{sub 2} concentration on the combustion behaviour of a fuel/oxidizer mixture. The material tested is a ternary mixture of lactose, starch, and potassium nitrate, which has already been used in an attempt to estimate heat release rate using the FM-Global Fire Propagation Apparatus. It provides a well-controlled combustion chamber to study the evolution of the combustion products when varying the O{sub 2} concentration, between air and low oxidizer conditions. Different chemical behaviours have been exhibited. When the O{sub 2} concentration was reduced beyond 18%, large variations were observed in the CO{sub 2} and CO concentrations. This critical O{sub 2} concentration seems to be the limit before which the material only uses its own oxidizer to react. On the other hand, mass loss did not highlight this change in chemical reactions and remained similar whatever the test conditions. This presumes that the oxidation of CO into CO{sub 2} are due to reactions occurring in the gas phase especially for large O{sub 2} concentrations. This actual behaviour can be verified using a simplified flammability limit model adapted for the current work. Finally, a sensitivity analysis has been carried out to underline the influence of CO concentration in the evaluation of heat release rate using typical calorimetric methods. The results of this study provide a critical basis for the investigation of the combustion of a fuel/oxidizer mixture and for the validation of future numerical models. (author)

  2. Effect of oxygen concentration on human embryo development evaluated by time-lapse monitoring

    DEFF Research Database (Denmark)

    Ingerslev, Hans Jakob; Hindkjær, Johnny Juhl; Kirkegaard, Kirstine

    2012-01-01

    recently demonstrated to occur from first cleavage cycle in mice using time-lapse microscopy, with the largest impact on the pre-compaction stages. However, embryonic development in mice differs in many aspects from human embryonic development. The objective of this retrospective, descriptive study...... was to evaluate the influence of oxygen tension on human pre-implantation development using time-lapse monitoring. Materials and methods: Human embryos were cultured to the blastocyst stage in a time-lapse incubator (EmbryoScope™) in 20% O2 (group 1), 20% O2 for 24 hours followed by culture in 5% O2 (group 2......) or in 5% O2 (group 3). Eligible were patients with age 8 oocytes retrieved. Group 1 consisted of 120 IVF/ICSI embryos from 26 patients recruited to a study conducted to evaluate the safety of the time-lapse incubator by randomising 1:1 embryos from a patient to culture...

  3. Design a Wearable Device for Blood Oxygen Concentration and Temporal Heart Beat Rate

    Science.gov (United States)

    Myint, Cho Zin; Barsoum, Nader; Ing, Wong Kiing

    2010-06-01

    The wireless network technology is increasingly important in healthcare as a result of the aging population and the tendency to acquire chronic disease such as heart attack, high blood pressure amongst the elderly. A wireless sensor network system that has the capability to monitor physiological sign such as SpO2 (Saturation of Arterial Oxygen) and heart beat rate in real-time from the human's body is highlighted in this study. This research is to design a prototype sensor network hardware, which consists of microcontroller PIC18F series and transceiver unit. The sensor is corporate into a wearable body sensor network which is small in size and easy to use. The sensor allows a non invasive, real time method to provide information regarding the health of the body. This enables a more efficient and economical means for managing the health care of the population.

  4. Tolerance of Oncomelania hupensis quadrasi to varying concentrations of dissolved oxygen and organic pollution*

    Science.gov (United States)

    Garcia, Rolando G.

    1972-01-01

    Ecological investigations were made of habitats containing natural populations of the snail Oncomelania hupensis quadrasi and of habitats free from the snail in the island of Leyte, Philippines. This species of snail is a vector of Schistosoma japonicum in the Philippines. Snail-infested habitats had dissolved oxygen levels of 3.8-9.85 ppm but snail-free habitats had levels of only 0.08-3.6 ppm. Snail-infested habitats were less polluted by organic matter than habitats that were snail-free. Larger numbers of chlorophyll-bearing algae were present in both the water and the soil of snail-infested habitats. Other factors, including temperature, pH, hydrogen carbonate alkalinity, and relative humidity, were also investigated. PMID:4538906

  5. Sodium fire test at broad ranges of temperature and oxygen concentration. 4. Low temperature sodium spray fire tests

    International Nuclear Information System (INIS)

    Kawata, Koji; Miyahara, Shinya

    2005-08-01

    Sodium spray fire tests at the initial sodium temperature of 250degC were conducted under the atmospheric conditions of air and 3% oxygen containing nitrogen to determine the sodium burning rate and the aerosol release fraction and compare them with the test results at the initial sodium temperature of 500degC in air atmosphere. In the tests, sodium was supplied using a commercial spray nozzle into a stainless steel vessel of 100 m 3 volume (SOLFA-2). The sodium burning rate was calculated from two independent methods: the consumption rate of oxygen in the vessel and the enthalpy change of vessel components during the test. The aerosol release fraction was determined from the comparison between the measured aerosol concentrations and the calculated ones by the ABC-INTG code. The main conclusions were as follows, (1) In air atmosphere, a) sodium droplets ignited instantaneously and the spray fire was observed, and b) the sodium burning rate was about 440 g-Na/s and the fraction of supplied sodium was about 70%. (2) In 3% oxygen containing nitrogen, a) ignition of sodium droplets was not observed, and b) the sodium burning rate was about 44 g-Na/s and the fraction of supplied sodium was less than 10%. (author)

  6. Revealing mechanisms of selective, concentration-dependent potentials of 4-hydroxy-2-nonenal to induce apoptosis in cancer cells through inactivation of membrane-associated catalase.

    Science.gov (United States)

    Bauer, Georg; Zarkovic, Neven

    2015-04-01

    Tumor cells generate extracellular superoxide anions and are protected against superoxide anion-mediated intercellular apoptosis-inducing signaling by the expression of membrane-associated catalase. 4-Hydroxy-2-nonenal (4-HNE), a versatile second messenger generated during lipid peroxidation, has been shown to induce apoptosis selectively in malignant cells. The findings described in this paper reveal the strong, concentration-dependent potential of 4-HNE to specifically inactivate extracellular catalase of tumor cells both indirectly and directly and to consequently trigger apoptosis in malignant cells through superoxide anion-mediated intercellular apoptosis-inducing signaling. Namely, 4-HNE caused apoptosis selectively in NOX1-expressing tumor cells through inactivation of their membrane-associated catalase, thus reactivating subsequent intercellular signaling through the NO/peroxynitrite and HOCl pathways, followed by the mitochondrial pathway of apoptosis. Concentrations of 4-HNE of 1.2 µM and higher directly inactivated membrane-associated catalase of tumor cells, whereas at lower concentrations, 4-HNE triggered a complex amplificatory pathway based on initial singlet oxygen formation through H2O2 and peroxynitrite interaction. Singlet-oxygen-dependent activation of the FAS receptor and caspase-8 increased superoxide anion generation by NOX1 and amplification of singlet oxygen generation, which allowed singlet-oxygen-dependent inactivation of catalase. 4-HNE and singlet oxygen cooperate in complex autoamplificatory loops during this process. The finding of these novel anticancer pathways may be useful for understanding the role of 4-HNE in the control of malignant cells and for the optimization of ROS-dependent therapeutic approaches including antioxidant treatments. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Effects of inoculum type and bulk dissolved oxygen concentration on achieving partial nitrification by entrapped-cell-based reactors.

    Science.gov (United States)

    Rongsayamanont, Chaiwat; Limpiyakorn, Tawan; Khan, Eakalak

    2014-07-01

    An entrapment of nitrifiers into gel matrix is employed as a tool to fulfill partial nitrification under non-limiting dissolved oxygen (DO) concentrations in bulk solutions. This study aims to clarify which of these two attributes, inoculum type and DO concentration in bulk solutions, is the decisive factor for partial nitrification in an entrapped-cell based system. Four polyvinyl alcohol entrapped inocula were prepared to have different proportions of nitrite-oxidizing bacteria (NOB) and nitrite-oxidizing activity. At a DO concentration of 3 mg l(-1), the number of active NOB cells in an inoculum was the decisive factor for partial nitrification enhancement. However, when the DO concentration was reduced to 2 mg l(-1), all entrapped cell inocula showed similar degrees of partial nitrification. The results suggested that with the lower bulk DO concentration, the preparation of entrapped cell inocula is not useful as the DO level becomes the decisive factor for achieving partial nitrification. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Non-diagonal processes of singlet and ordinary quark production

    International Nuclear Information System (INIS)

    Bejlin, V.A.; Vereshkov, G.M.; Kuksa, V.I.

    1995-01-01

    Non-diagonal processes of singlet and ordinary quark production are analyzed in the model where the down singlet quark mixes with the ordinary ones. The possibility of experimental selection of h-quark effects is demonstrated

  9. Virucidal Nanofiber Textiles Based on Photosensitized Production of Singlet Oxygen

    Czech Academy of Sciences Publication Activity Database

    Lhotáková, Y.; Plištil, L.; Morávková, A.; Kubát, Pavel; Lang, Kamil; Forstová, J.; Mosinger, J.

    2012-01-01

    Roč. 7, č. 11 (2012), e49226 E-ISSN 1932-6203 R&D Projects: GA ČR GAP208/10/1678 Institutional support: RVO:61388955 ; RVO:61388980 Keywords : photosynthesis * biomaterials * nanofiber textiles Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.730, year: 2012

  10. Crossed Optical Fiber Sensor Arrays for High-Spatial-Resolution Sensing: Application to Dissolved Oxygen Concentration Measurements

    Directory of Open Access Journals (Sweden)

    M. Veronica Rigo

    2012-01-01

    Full Text Available Optical fiber sensors using luminescent probes located along an optical fiber in the cladding of this fiber are of great interest for monitoring physical and chemical properties in their environment. The interrogation of a luminophore with a short laser pulse propagating through the fiber core allows for the measurement of the location of these luminophores. To increase the spatial resolution of such a measurements and to measure multiple analytes and properties in a confined space, a crossed optical fiber sensing platform can be employed. Here we describe the application of this platform to measuring the concentration of dissolved oxygen. The sensor is based on luminescence quenching of a ruthenium complex immobilized in a highly crosslinked film and covalently attached to the optical fibers. Both luminescence-intensity and luminescence-lifetime changes of the sensor molecules in response to changes in the concentration of oxygen dissolved in water are reported. For luminescence-intensity measurements, a second adjacent sensor region is employed as reference to account for laser pulse energy fluctuations. Enhanced quenching response in water is demonstrated by the use of organically modified poly(ethylene glycol precursors, which increase the hydrophobicity of the film surface.

  11. Biological phosphorus and nitrogen removal in sequencing batch reactors: effects of cycle length, dissolved oxygen concentration and influent particulate matter.

    Science.gov (United States)

    Ginige, Maneesha P; Kayaalp, Ahmet S; Cheng, Ka Yu; Wylie, Jason; Kaksonen, Anna H

    2013-01-01

    Removal of phosphorus (P) and nitrogen (N) from municipal wastewaters is required to mitigate eutrophication of receiving water bodies. While most treatment plants achieve good N removal using influent carbon (C), the use of influent C to facilitate enhanced biological phosphorus removal (EBPR) is poorly explored. A number of operational parameters can facilitate optimum use of influent C and this study investigated the effects of cycle length, dissolved oxygen (DO) concentration during aerobic period and influent solids on biological P and N removal in sequencing batch reactors (SRBs) using municipal wastewaters. Increasing cycle length from 3 to 6 h increased P removal efficiency, which was attributed to larger portion of N being removed via nitrite pathway and more biodegradable organic C becoming available for EBPR. Further increasing cycle length from 6 to 8 h decreased P removal efficiencies as the demand for biodegradable organic C for denitrification increased as a result of complete nitrification. Decreasing DO concentration in the aerobic period from 2 to 0.8 mg L(-1) increased P removal efficiency but decreased nitrification rates possibly due to oxygen limitation. Further, sedimented wastewater was proved to be a better influent stream than non-sedimented wastewater possibility due to the detrimental effect of particulate matter on biological nutrient removal.

  12. Radiation-induced strand-breaks and DNA-protein crosslinks depend predominantly on the dose, oxygen concentration and repair time

    International Nuclear Information System (INIS)

    Wheeler, K.T.; Miyagi, Y.; Zhang, H.

    1995-01-01

    It has been known for many years that the DNA damage produced by ionizing radiation depends upon the oxygen concentration around the DNA. For example, the number of DNA strand-breaks (SBs) formed per unit dose decreases at low oxygen concentrations, and the number of DNA-protein crosslinks formed per unit dose increases at low oxygen concentrations. If radiation-induced SBs and DPCs are to be useful for detecting and/or quantifying hypoxic cells in solid tumors, the formation of these lesions must depend predominantly on the oxygen concentration around the DNA. All other physical, biological, and physiological factors must either be controllable or have little influence on the assay used to measure these lesions. This paper is a summary of the authors' recent experiments to determine if the radiation-induced SBs and DPCs measured by alkaline elution may be used to estimate the hypoxic fraction or fractional hypoxic volume of solid tumors

  13. Simultaneous denitrification and phosphorus removal by Agrobacterium sp. LAD9 under varying oxygen concentration.

    Science.gov (United States)

    Ma, Tao; Chen, Qian; Gui, Mengyao; Li, Can; Ni, Jinren

    2016-04-01

    Although efficient aerobic denitrification has received increasing attention, few studies have been made on simultaneous denitrification and phosphorus removal (SDPR) under aerobic condition. In this study, SDPR by an efficient aerobic denitrifier, Agrobacterium sp. LAD9, was firstly demonstrated. High nitrate and phosphorus removal rates of 7.50 and 1.02 mg L(-1) h(-1) were achieved in wide range of O2 concentration from 5.92 to 20.02 mg L(-1). The N2O production would be inhibited as O2 concentration exceeded 11.06 mg L(-1), while the phosphorus removal efficiency would be generally improved with increasing O2 concentration. (15)N mass spectrometry revealed that nitrogen removal accorded with the typical aerobic denitrification pathway, while (31)P nuclear magnetic resonance spectroscopy ((31)P NMR) indicated the fate of phosphorus to cells, extracellular polymeric substances (EPS), and polyphosphate (poly-P) of the denitrifier. EPS acted as a reservoir of phosphorus and the transformation of poly-P was dynamic and depended on initial orthophosphate (ortho-P) content. The aerobic SDPR would greatly simplify the conventional wastewater treatment processes which required separated considerations of nitrogen and phosphorus removal.

  14. Time required for partial pressure of arterial oxygen equilibration during mechanical ventilation after a step change in fractional inspired oxygen concentration.

    Science.gov (United States)

    Cakar, N; Tuŏrul, M; Demirarslan, A; Nahum, A; Adams, A; Akýncý, O; Esen, F; Telci, L

    2001-04-01

    To determine the time required for the partial pressure of arterial oxygen (PaO2) to reach equilibrium after a 0.20 increment or decrement in fractional inspired oxygen concentration (FIO2) during mechanical ventilation. A multi-disciplinary ICU in a university hospital. Twenty-five adult, non-COPD patients with stable blood gas values (PaO2/FIO2 > or = 180 on the day of the study) on pressure-controlled ventilation (PCV). Following a baseline PaO2 (PaO2b) measurement at FIO2 = 0.35, the FIO2 was increased to 0.55 for 30 min and then decreased to 0.35 without any other change in ventilatory parameters. Sequential blood gas measurements were performed at 3, 5, 7, 9, 11, 15, 20, 25 and 30 min in both periods. The PaO2 values measured at the 30th min after a step change in FIO2 (FIO2 = 0.55, PaO2[55] and FIO2 = 0.35, PaO2[35]) were accepted as representative of the equilibrium values for PaO2. Each patient's rise and fall in PaO2 over time, PaO2(t), were fitted to the following respective exponential equations: PaO2b + (PaO2[55]-PaO2b)(1-e-kt) and PaO2[55] + (PaO2[35]-PaO2[55])(e-kt) where "t" refers to time, PaO2[55] and PaO2[35] are the final PaO2 values obtained at a new FIO2 of 0.55 and 0.35, after a 0.20 increment and decrement in FIO2, respectively. Time constant "k" was determined by a non-linear fitting curve and 90% oxygenation times were defined as the time required to reach 90% of the final equilibrated PaO2 calculated by using the non-linear fitting curves. Time constant values for the rise and fall periods were 1.01 +/- 0.71 min-1, 0.69 +/- 0.42 min-1, respectively, and 90% oxygenation times for rises and falls in PaO2 periods were 4.2 +/- 4.1 min-1 and 5.5 +/- 4.8 min-1, respectively. There was no significant difference between the rise and fall periods for the two parameters (p > 0.05). We conclude that in stable patients ventilated with PCV, after a step change in FIO2 of 0.20, 5-10 min will be adequate for obtaining a blood gas sample to measure a Pa

  15. Recycling and imaging of nuclear singlet hyperpolarization

    DEFF Research Database (Denmark)

    Pileio, Giuseppe; Bowen, Sean; Laustsen, Christoffer

    2013-01-01

    observation of the same batch of polarized nuclei over a period of 30 min and more. We report a recycling protocol in which the enhanced nuclear polarization achieved by dissolution-DNP is observed with full intensity and then returned to singlet order. MRI experiments may be run on a portion of the available...

  16. Singlet fermionic dark matter with Veltman conditions

    Science.gov (United States)

    Kim, Yeong Gyun; Lee, Kang Young; Nam, Soo-hyeon

    2018-07-01

    We reexamine a renormalizable model of a fermionic dark matter with a gauge singlet Dirac fermion and a real singlet scalar which can ameliorate the scalar mass hierarchy problem of the Standard Model (SM). Our model setup is the minimal extension of the SM for which a realistic dark matter (DM) candidate is provided and the cancellation of one-loop quadratic divergence to the scalar masses can be achieved by the Veltman condition (VC) simultaneously. This model extension, although renormalizable, can be considered as an effective low-energy theory valid up to cut-off energies about 10 TeV. We calculate the one-loop quadratic divergence contributions of the new scalar and fermionic DM singlets, and constrain the model parameters using the VC and the perturbative unitarity conditions. Taking into account the invisible Higgs decay measurement, we show the allowed region of new physics parameters satisfying the recent measurement of relic abundance. With the obtained parameter set, we predict the elastic scattering cross section of the new singlet fermion into target nuclei for a direct detection of the dark matter. We also perform the full analysis with arbitrary set of parameters without the VC as a comparison, and discuss the implication of the constraints by the VC in detail.

  17. Update on scalar singlet dark matter

    NARCIS (Netherlands)

    Cline, J.M.; Scott, P.; Kainulainen, K.; Weniger, C.

    2013-01-01

    One of the simplest models of dark matter is where a scalar singlet field S comprises some or all of the dark matter and interacts with the standard model through an vertical bar H vertical bar S-2(2) coupling to the Higgs boson. We update the present limits on the model from LHC searches for

  18. Numerical simulation of the oxygen concentration distribution in silicon melt for different crystal lengths during Czochralski growth with a transverse magnetic field

    Science.gov (United States)

    Chen, Jyh-Chen; Chiang, Pei-Yi; Nguyen, Thi Hoai Thu; Hu, Chieh; Chen, Chun-Hung; Liu, Chien-Cheng

    2016-10-01

    A three-dimensional simulation model is used to study the oxygen concentration distribution in silicon crystal during the Czochralski growth process under a transverse uniform magnetic field. The flow, temperature, and oxygen concentration distributions inside the furnace are calculated for different crystal lengths. There is significant variation in the flow structure in the melt with the growth length. The results show that in the initial stages, there is a decrease in the oxygen concentration at the crystal-melt interface as the length of the growing crystal increases. As the crystal lengthens further, a minimum value is reached after which the oxygen concentration increases continuously. This trend is consistent with that shown in the experimental results. The variation of the oxygen concentration with the growth length is strongly related to the depth of the melt in the crucible and the flow structure inside the melt. Better uniformity of the axial oxygen concentration can be achieved by proper adjustment of the crucible rotation rate during the growth process.

  19. The effect of chlorine and oxygen concentrations on the removal of mercury at an FGD-batch reactor

    Energy Technology Data Exchange (ETDEWEB)

    Carolina Acuna-Caro; Kevin Brechtel; Guenter Scheffknecht; Manuel Brass [University of Stuttgart, Stuttgart (Germany). Institute of Process Engineering and Power Plant Technology (IVD)

    2009-12-15

    A series of laboratory scale experiments were conducted in an FGD-batch reactor. A synthetic flue gas was produced and directed through a CaCO{sub 3} suspension contained in a glass reactor vessel. The suspension temperature was set at 54{sup o}C through a water bath. In order to observe the distribution of mercury species in the system, solid, liquid and gaseous samples were taken and analysed. For gaseous mercury determination, continuous measurements were carried out, up and downstream the reactor. Furthermore, the concentration of chlorine in the scrubber solution of the system was varied from 0 to 62 g/l under different oxidative conditions. In a first approach, a concentration drop of elemental mercury coming out of the system was observed. The latter occurs only when high concentrations of Cl{sup -} are present, combined with a high O{sub 2} availability in the scrubber. It was also observed that mercury species distribution in the different phases varies, depending on the available chemical form of chlorine and oxygen concentration. 14 refs., 7 figs., 1 tab.

  20. Efficacy of a portable oxygen concentrator with pulsed delivery for treatment of hypoxemia during equine field anesthesia.

    Science.gov (United States)

    Coutu, Paige; Caulkett, Nigel; Pang, Daniel; Boysen, Søren

    2015-09-01

    Hypoxemia is common during equine field anesthesia. Our hypothesis was that oxygen therapy from a portable oxygen concentrator would increase PaO2 during field anesthesia compared with the breathing of ambient air. Prospective clinical study. Fifteen yearling (250 - 400 kg) horses during field castration. Horses were maintained in dorsal recumbency during anesthesia with an intravenous infusion of 2000 mg ketamine and 500 mg xylazine in 1 L of 5% guaifenesin. Arterial samples for blood gas analysis were collected immediately post-induction (PI), and at 15 and 30 minutes PI. The control group (n = 6) breathed ambient air. The treatment group (n = 9) were administered pulsed-flow oxygen (192 mL per bolus) by nasal insufflation during inspiration for 15 minutes PI, then breathed ambient air. The study was performed at 1300 m above sea level. One-way and two-way repeated-measures anova with post-hoc Bonferroni tests were used for within and between-group comparisons, respectively. Significance was set at p ≤ 0.05. Mean ± SD PaO2 in controls at 0, 15 and 30 minutes PI were 46 ± 7 mmHg (6.1 ± 0.9 kPa), 42 ± 9 mmHg (5.6 ± 1.1 kPa), and 48 ± 7 mmHg (6.4 ± 0.1 kPa), respectively (p = 0.4). In treatment animals, oxygen administration significantly increased PaO2 at 15 minutes PI to 60 ± 13 mmHg (8.0 ± 1.7 kPa), compared with baseline values of 46 ± 8 mmHg (6.1 ± 1 kPa) (p = 0.007), and 30 minute PI values of 48 ± 7 mmHg (6.5 ± 0.9 kPa) (p = 0.003). These data show that a pulsed-flow delivery of oxygen can increase PaO2 in dorsally recumbent horses during field anesthesia with ketamine-xylazine-guaifenesin. The portable oxygen concentrator may help combat hypoxemia during field anesthesia in horses. © 2015 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.

  1. A hyperoxic lung injury model in premature rabbits: the influence of different gestational ages and oxygen concentrations.

    Directory of Open Access Journals (Sweden)

    Roberta Munhoz Manzano

    Full Text Available BACKGROUND: Many animal models have been developed to study bronchopulmonary dysplasia (BPD. The preterm rabbit is a low-cost, easy-to-handle model, but it has a high mortality rate in response to the high oxygen concentrations used to induce lung injury. The aim of this study was to compare the mortality rates of two models of hyperoxia-induced lung injury in preterm rabbits. METHODS: Pregnant New Zealand white rabbits were subjected to caesarean section on gestational day 28 or 29 (full term  = 31 days. The premature rabbits in the 28-day gestation group were exposed to room air or FiO₂ ≥95%, and the rabbits in the 29-day gestation group were exposed to room air or FiO₂  = 80% for 11 days. The mean linear intercept (Lm, internal surface area (ISA, number of alveoli, septal thickness and proportion of elastic and collagen fibers were quantified. RESULTS: The survival rates in the 29-day groups were improved compared with the 28-day groups. Hyperoxia impaired the normal development of the lung, as demonstrated by an increase in the Lm, the septal thickness and the proportion of elastic fibers. Hyperoxia also decreased the ISA, the number of alveoli and the proportion of collagen fibers in the 28-day oxygen-exposed group compared with the control 28-day group. A reduced number of alveoli was found in the 29-day oxygen exposed animals compared with the control 29-day group. CONCLUSIONS: The 29-day preterm rabbits had a reduced mortality rate compared with the 28-day preterm rabbits and maintained a reduction in the alveoli number, which is comparable to BPD in humans.

  2. Effect of varying concentrations of caffeine and ascorbic acid on the radiosensitivity of barley seed irradiated in oxygenated or oxygen-free hydration medium at 25 and 3700C

    International Nuclear Information System (INIS)

    Afzal, S.M.J.; Kesavan, P.C.

    1977-01-01

    The modification of radiosensitivity of barley seed with 1.75 x 10 -3 M and 3.8 x 10 -3 M concentrations of caffeine and ascorbic acid during irradiation in oxygenated and oxygen-free hydration medium was studied at 25 and 37 0 C, respectively. Both concentrations of caffeine and ascorbic acid afforded protection against oxic radiation damage which was maximal at 25 0 C. Caffeine effectively potentiated the anoxic component of damage but ascorbic acid had no influence at all. At 25 0 C there was no concentration-dependent effect of caffeine or ascorbic acid. At 37 0 C, there was no effect, whatsoever, of either concentration of ascorbic acid, whereas caffeine dramatically potentiated the radiation damage under both oxygenated and oxygen-free conditions, and the magnitude of potentiation was concentration-dependent. The possible reactivity of caffeine and ascorbic acid towards the precursors of oxygen-dependent and -independent components of damage in determining the mode and magnitudes of modification is discussed briefly. (author)

  3. Tertiary treatment of textile wastewater with combined media biological aerated filter (CMBAF) at different hydraulic loadings and dissolved oxygen concentrations

    International Nuclear Information System (INIS)

    Liu Fang; Zhao Chaocheng; Zhao Dongfeng; Liu Guohua

    2008-01-01

    An up-flow biological aerated filter packed with two layers media was employed for tertiary treatment of textile wastewater secondary effluent. Under steady state conditions, good performance of the reactor was achieved and the average COD, NH 4 + -N and total nitrogen (TN) in the effluent were 31, 2 and 8 mg/L, respectively. For a fixed dissolved oxygen (DO) concentration, an increase of hydraulic loading resulted in a decrease in substrate removal. With the increase of hydraulic loadings from 0.13 to 0.78 m 3 /(m 2 h), the removal efficiencies of COD, NH 4 + -N and TN all decreased, which dropped from 52 to 38%, from 90 to 68% and from 45 to 33%, respectively. In addition, the results also confirmed that the increase of COD and NH 4 + -N removal efficiencies resulted from the increase of DO concentrations, but this variation trend was not observed for TN removal. With the increase of DO concentrations from 2.4 to 6.1 mg/L, the removal efficiencies of COD and NH 4 + -N were 39-53% and 64-88%, whenas TN removal efficiencies increased from 39 to 42% and then dropped to 35%

  4. Modelling daily dissolved oxygen concentration using least square support vector machine, multivariate adaptive regression splines and M5 model tree

    Science.gov (United States)

    Heddam, Salim; Kisi, Ozgur

    2018-04-01

    In the present study, three types of artificial intelligence techniques, least square support vector machine (LSSVM), multivariate adaptive regression splines (MARS) and M5 model tree (M5T) are applied for modeling daily dissolved oxygen (DO) concentration using several water quality variables as inputs. The DO concentration and water quality variables data from three stations operated by the United States Geological Survey (USGS) were used for developing the three models. The water quality data selected consisted of daily measured of water temperature (TE, °C), pH (std. unit), specific conductance (SC, μS/cm) and discharge (DI cfs), are used as inputs to the LSSVM, MARS and M5T models. The three models were applied for each station separately and compared to each other. According to the results obtained, it was found that: (i) the DO concentration could be successfully estimated using the three models and (ii) the best model among all others differs from one station to another.

  5. Physical and Instrumental Considerations in the Use of Lithium Phthalocyanine for Measurements of the Concentration of the Oxygen

    Science.gov (United States)

    Smirnov, A. I.; Norby, S. W.; Walczak, T.; Liu, K. J.; Swartz, H. M.

    The use of crystals of lithium phthalocyanine (LiPc) to measure the concentration of oxygen in vivo and in vitro by electron paramagnetic resonance leads to experimental constraints due to the very narrow EPR lines that may occur (as narrow as 11-13 mG in the absence of O 2), distortions induced by the automatic frequency control system, anisotropy in the spectra (orientation-dependent linewidth is 11-17 mG in the absence of O 2), microwave power saturation, and the effect of physiological motion. These constraints can be overcome if recognized. This article highlights the experimental and theoretical basis of these properties of the EPR signal of LiPc and suggests some technical solutions. It is most important to recognize that paramagnetic species such as LiPc present problems that are not commonly encountered in EPR spectroscopy.

  6. Role of N2 molecules in pulse discharge production of I atoms for a pulsed chemical oxygen-iodine laser

    International Nuclear Information System (INIS)

    Kochetov, I V; Napartovich, A P; Vagin, N P; Yuryshev, N N

    2011-01-01

    A pulsed electric discharge is the most effective means to turn chemical oxygen-iodine laser (COIL) operation into the pulse mode by fast production of iodine atoms. Experimental studies and numerical simulations are performed on a pulsed COIL initiated by an electric discharge in a mixture CF 3 I : N 2 : O 2 ( 3 X) : O 2 (a 1 Δ g ) flowing out of a chemical singlet oxygen generator. A transverse pulsed discharge is realized at various iodide pressures. The model comprises a system of kinetic equations for neutral and charged species, the electric circuit equation, the gas thermal balance equation and the photon balance equation. Reaction rate coefficients for processes involving electrons are repeatedly re-calculated by the electron Boltzmann equation solver when the plasma parameters are changed. The processes accounted for in the Boltzmann equation include direct and stepwise excitation and ionization of atoms and molecules, dissociation of molecules, electron attachment processes, electron-ion recombination, electron-electron collisions and second-kind collisions. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the singlet oxygen chemical generator. A conclusion is drawn about satisfactory agreement between the theory and the experiment.

  7. Determination of optical properties, drug concentration, and tissue oxygenation in human pleural tissue before and after Photofrin-mediated photodynamic therapy

    Science.gov (United States)

    Ong, Yi Hong; Padawer-Curry, Jonah; Finlay, Jarod C.; Kim, Michele M.; Dimofte, Andreea; Cengel, Keith; Zhu, Timothy C.

    2018-02-01

    PDT efficacy depends on the concentration of photosensitizer, oxygen, and light delivery in patient tissues. In this study, we measure the in-vivo distribution of important dosimetric parameters, namely the tissue optical properties (absorption μa (λ) and scattering μs ' (λ) coefficients), photofrin concentration (cphotofrin), blood oxygen saturation (%StO2), and total hemoglobin concentration (THC), before and after PDT. We characterize the inter- and intra-patient heterogeneity of these quantities and explore how these properties change as a result of PDT treatment. The result suggests the need for real-time dosimetry during PDT to optimize the treatment condition depending on the optical and physiological properties.

  8. Magnetic properties of singlet ground state systems

    International Nuclear Information System (INIS)

    Diederix, K.M.

    1979-01-01

    Experiments are described determining the properties of a magnetic system consisting of a singlet ground state. Cu(NO 3 ) 2 .2 1/2H 2 O has been studied which is a system of S = 1/2 alternating antiferromagnetic Heisenberg chains. The static properties, spin lattice relaxation time and field-induced antiferromagnetically ordered state measurements are presented. Susceptibility and magnetic cooling measurements of other compounds are summarised. (Auth.)

  9. Multi-regional investigation of the relationship between functional MRI blood oxygenation level dependent (BOLD activation and GABA concentration.

    Directory of Open Access Journals (Sweden)

    Ashley D Harris

    Full Text Available Several recent studies have reported an inter-individual correlation between regional GABA concentration, as measured by MRS, and the amplitude of the functional blood oxygenation level dependent (BOLD response in the same region. In this study, we set out to investigate whether this coupling generalizes across cortex. In 18 healthy participants, we performed edited MRS measurements of GABA and BOLD-fMRI experiments using regionally related activation paradigms. Regions and tasks were the: occipital cortex with a visual grating stimulus; auditory cortex with a white noise stimulus; sensorimotor cortex with a finger-tapping task; frontal eye field with a saccade task; and dorsolateral prefrontal cortex with a working memory task. In contrast to the prior literature, no correlation between GABA concentration and BOLD activation was detected in any region. The origin of this discrepancy is not clear. Subtle differences in study design or insufficient power may cause differing results; these and other potential reasons for the discrepant results are discussed. This negative result, although it should be interpreted with caution, has a larger sample size than prior positive results, and suggests that the relationship between GABA and the BOLD response may be more complex than previously thought.

  10. Chemistry and Mechanism of Interaction Between Molybdenite Concentrate and Sodium Chloride When Heated in the Presence of Oxygen

    Science.gov (United States)

    Aleksandrov, P. V.; Medvedev, A. S.; Imideev, V. A.; Moskovskikh, D. O.

    2017-04-01

    Roasting of molybdenum concentrates with sodium chloride has high potential and can be an alternative to oxidizing roasting and autoclave leaching; however, the chemistry and mechanism are poorly known. The chemical mechanism of the roasting process between molybdenite concentrate and sodium chloride in the presence of atmospheric oxygen is proposed. It is demonstrated that the process occurs through molybdenite oxidation, up to molybdenum trioxide, with subsequent formation of sodium polymolybdates and molybdenum dioxydichloride from molybdenum trioxide. It is found that the formation of water-soluble sodium polymolybdates from molybdenum trioxide stops over time due to passivation of sodium chloride surface by polymolybdates. It is proved experimentally that preliminary grinding of the mixture in a furnace charge leads to an increase in the polymolybdate fraction of the roasting products, which constitutes approximately 65 pct of molybdenum initially in the roasted mixture against 20 to 22 pct in a nonground mixture (or 75 to 77 pct against 30 to 33 pct of molybdenum in calcine). For the first time, the presence of the Na2S2O7 phase in the calcine was confirmed experimentally. The suggested mechanism gives possible explanations for the sharp increase of MoO2Cl2 formation within the temperature range of 673 K to 723 K (400 °C to 450 °C) that is based on the catalytic reaction of molybdenum dioxydichloride from the Na2S2O7 liquid phase as it runs in a melt.

  11. Defect chemistry modelling of oxygen-stoichiometry, vacancy concentrations, and conductivity of (La1-xSrx)(y)MnO3 +/-delta

    DEFF Research Database (Denmark)

    Poulsen, F.W.

    2000-01-01

    model, based on delocalised electrons, electron holes and all B-ions being trivalent is given in Appendix A. The sequential mathematical method allows us to calculate the high temperature oxygen partial pressure dependent properties of (La1-xSrx)(y)MnO3+/-delta in a unified manner irrespective...... are calculated by the small polaron model containing only ionic species - the B-ion may be Mn-B' (Mn2+), Mn-B(x) (Mn3+), and Mn-B(Mn4+). The A/B-ratio = y greatly influences the oxygen stoichiometry, oxygen ion vacancy- and cation vacancy concentrations and the total conductivity. Calculations are given...

  12. The effects of health education given by nurses to COPD patients on the daily oxygen concentrator usage time.

    Science.gov (United States)

    Doğan, Uğur; Ovayolu, Nimet

    2017-01-01

    Long-term oxygen therapy is the most effective method which has been shown to prolong the lifespan in people with COPD. The aim of the study was to investigate the effects of health education given by nurses to patients with COPD on the daily oxygen concentrator (OC) usage time. The study was carried out in a State Hospital, Turkey, between July and November 2015. After given consent to the study, participants were divided into intervention and control groups by simple random sampling method. Then data forms were filled during face-to-face interview. Firstly, the data describing patients' arrival times were collected retrospectively. Afterwards, the patients from the intervention group were educated through educational booklets prepared by the researchers. They were phoned in the weeks 4, 8 and 12th for problems they might have encountered during the use of OC. After the 14th week, data forms of patients from the both groups were filled again; the results were compared with previous clinical findings. Data were analysed using SPSS 15.0 for Windows. It was determined that 95.5% of patients did not get information about the use of OC. Daily OC usage time (hour) by patients in the intervention group firstly amounted to 5.69 ± 3.90, later on to 11.94 ± 4.73 (p < 0.05). Whereas when clinical findings concerning pre- and post educational periods were compared; a significant improvement in PaO₂, PaCO2, FEV₁ and SaO₂ of patients in the intervention group (p<0.05) was shown, contrary to the control group. It may be recommended that patients receive continuous education and close monitoring of their results.

  13. Irradiation of mammalian cells in the presence of diamide and low concentrations of oxygen at conventional and at ultrahigh dose rates

    International Nuclear Information System (INIS)

    Clark, E.P.; Michaels, H.B.; Peterson, E.C.; Epp, E.R.

    1983-01-01

    The response of cultured CHO cells to ultrahigh-dose-radiation (approx.10 9 Gy/sec) has been previously studied extensively using the thin-layer cell-handling technique developed in this laboratory. When the cells are equilibrated with a low concentration of oxygen, e.g., 0.44% O 2 , a breaking survival curve, due to radiolytic depletion of the oxygen, is observed. Hypoxic cells irradiated in the presence of the nitroimidazoles (e.g., misonidazole) are sensitized at ultrahigh dose rates in a dose-modifying manner, similar to that observed at conventional dose rates. These radiosensitizer compounds, if present in cells equilibrated with a low concentration of oxygen, prevent the breaking behavior of the survival curve, an observation believed to be due to the sensitizer interfering with the oxygen depletion process, leaving oxygen free to sensitize. Such experiments have recently been extended to studies with diamide, which, unlike the other sensitizers tested, acts primarily as a shoulder-modifying rather than a dose-modifying agent in hypoxic mammalian cells. These data indicate that diamide is active as a sensitizer at ultrahigh dose rates in a manner similar to that observed at conventional dose rates, and does modify the shape of the breaking survival curve observed with low concentrations of oxygen

  14. Dissolved oxygen concentration profiles in the hyporheic zone through the use of a high density fiber optic measurement network

    Science.gov (United States)

    Reeder, W. J.; Quick, A. M.; Farrell, T. B.; Benner, S. G.; Feris, K. P.; Tonina, D.

    2013-12-01

    The hyporheic zone (HZ) is a potentially important source of the potent greenhouse gas, nitrous oxide (N2O); stream processes may account for up to 10% of global anthropogenic N2O emissions. However, mechanistic understanding and predictive quantification of this gas flux is hampered by complex temporally and spatially variable interactions between flow dynamics and biogeochemical processes. Reactive inorganic nitrogen (Nr) is typically present at low concentrations in natural stream waters, but many rural and urban streams suffer from an excess of Nr, typically in the form of ammonium (NH4+) and nitrate (NO3-). These reactive species are either assimilated by living biomass or transformed by microbial processes. The two primary microbial transformations of Nr are nitrification (NH4+ to NO3-) and denitrification (NO3- to N2). Denitrification, which occurs almost exclusively in the anoxic zone of the HZ, permanently removes between 30-70% of all Nr entering streams, other mechanisms may retain nitrogen. The mass transport of reactive species (i.e. O2, NO3- and N2O) by hyporheic flow strongly influences reaction rates, residence times, and subsequent N2O flux. By extension, stream flow and channel morphology presumably control, and may be effective predictors of, N2O generation rates. By recreating the stream processes in the University of Idaho flume, we are able to control the bed morphology, fluxes and residence times through the HZ and concentrations of Nr from exogenous (stream water) and endogenous (organic material in the streambed) sources. For the present experiment, the flume was divided into three streams, each with different morphologies (3, 6 and 9cm dunes) and all using the same source water. Stream water for this first experimental phase had no significant loading of Nr. As such, all reaction products were the result of endogenous sources of Nr. To measure dissolved oxygen (DO) concentrations we deployed 120 channels of a novel, fiber-optic optode

  15. Effect of different concentrations of oxygen on expression of sigma 1 receptor and superoxide dismutases in human colon adenocarcinoma cell lines.

    Science.gov (United States)

    Skrzycki, Michał; Czeczot, Hanna; Mielczarek-Puta, Magdalena; Otto-Ślusarczyk, Dagmara; Graboń, Wojciech

    2017-06-01

    Tumor cells due to distance from capillary vessels exist in different oxygenation conditions (anoxia, hypoxia, normoxia). Changes in cell oxygenation lead to reactive oxygen species production and oxidative stress. Sigma 1 receptor (Sig1R) is postulated to be stress responding agent and superoxide dismutases (SOD1 and SOD2) are key antioxidant enzymes. It is possible that they participate in tumor cells adaptation to different concentrations of oxygen. Evaluation of Sig1R, SOD1, and SOD2 expression in different concentrations of oxygen (1%, 10%, 21%) in colon adenocarcinoma cell lines. SW480 (primary adenocarcinoma) and SW620 (metastatic) cell lines were cultured in standard conditions in Dulbecco's modified Eagle's medium for 5 days, and next cultured in Hypoxic Chamber in 1% O 2 , 10% O 2 , 21% O 2 . Number of living cells was determined by trypan blue assay. Level of mRNA for Sig1R, SOD1, and SOD2 was determined by standard PCR method. Statistical analysis was conducted using Statistica 10.1 software. We observed significant changes in expression of Sig1R, SOD1, SOD2 due to different oxygen concentrations. ANOVA analysis revealed significant interactions between studied parameters mainly in hypoxia conditions in SW480 cells and between Sig1R and SOD2 in SW620 cells. It also showed that changes in expression of studied proteins depend significantly on type of the cell line. Changes of Sig1R and SOD2 expression point to mitochondria as main organelle responsible for survival of tumor cells exposed to hypoxia or oxidative stress. Studied proteins are involved in intracellular response to stress related with different concentrations of oxygen.

  16. Deuterium and oxygen-18 concentrations in rain and river waters from Minas Gerais, Sao Paulo and Parana States, Brazil

    International Nuclear Information System (INIS)

    Vieira, Oliveiro J.; Salati, Eneas

    1982-01-01

    The main object of this paper was to study the concentration of deuterium (D) and Oxygen-18 ( 18 O) in the rain and river waters from the States of Minas Gerais, Sao paulo and Parana. Monthly samples were prepared and analysed at the Centro de Energia Nuclear na Agricultura (CENA-ESALQ-USP) with the use of CH-4 ( 18 O) and GD-150 (D) mass spectrometers of Varian-Mat. In order to correlate the D and 18 O of the rain water the equation δD = 9.22 + 7.17δ18 was found. Considering the three equations separately it was observed that the parameter a = δD -bδ18 increases from the South to the North. For the Piracicaba River (city of Piracicaba only), the D and 18 O relationship was expressed by δD = -10.98 + 4.88δ18. The States of Minas Gerais and Sao Paulo can be divided according to the weight-average concentrations (δ18 m% 0 ). This division is not possible from Parana. Considering the average from the weight average concentration (annually and summer) for the three States, the annual average (D and 18 O) is slightly richer than the summer average, showing the importance of the amount effect, mainly for the States of Minas Gerais and Sao Paulo. The rivers studied had little variation in the 18 O concentrations with no definite periodicity. The rivers from the North of Minas Gerais are slightly richer in 18 O than the rivers from the South. The waters from Rio Grande in the South of Minas Gerais State are poorer in 18 O than the water of the same river in the 'Triangle'region. The δ18% 0 data for the rivers Grande, Parnaiba and Parana are very similar, so there is no way to compute the contribution of the first and the second rivers in the formation of the third. (author). 20 refs., 2 figs., 8 tabs

  17. Probing color-singlet exchange at D0

    International Nuclear Information System (INIS)

    Abbott, B.; Abolins, M.; Acharya, B.S.

    1997-07-01

    We present latest preliminary results on hard color-singlet exchange in proton-antiproton collisions. The fraction of dijet events produced via color-singlet exchange is measured as a function of jet transverse energy, dijet pseudorapidity separation, and proton-antiproton center-of-mass energy. These results are qualitatively consistent with a color-singlet fraction that increases with increasing quark-initiated processes

  18. Salicylic acid induces apoptosis in colon carcinoma cells grown in-vitro: Influence of oxygen and salicylic acid concentration

    Energy Technology Data Exchange (ETDEWEB)

    Zitta, Karina; Meybohm, Patrick; Bein, Berthold; Huang, Ying; Heinrich, Christin; Scholz, Jens; Steinfath, Markus; Albrecht, Martin, E-mail: Albrecht@anaesthesie.uni-kiel.de

    2012-04-15

    In solid tumors the hypoxic environment can promote tumor progression and resistance to therapy. Recently, acetylsalicylic acid a major component of analgesic drugs and its metabolite salicylic acid (SA) have been shown to reduce the risk of colon cancer, but the mechanisms of action remain still unclear. Here we elucidate the effects of physiologically relevant concentrations of SA on colon carcinoma cells (CaCo-2) grown under normoxic and hypoxic conditions. Western blotting, caspase-3/7 apoptosis assays, MTS cell-proliferation assays, LDH cytotoxicity assays and hydrogen peroxide measurements were performed to investigate the effects of 1 and 10 {mu}M SA on CaCo-2 cells grown under normoxic conditions and cells exposed to hypoxia. Under normoxic conditions, SA did not influence cell proliferation or LDH release of CaCo-2 cells. However, caspase-3/7 activity was significantly increased. Under hypoxia, cell proliferation was reduced and LDH release and caspase-3/7 activities were increased. None of these parameters was altered by the addition of SA under hypoxic conditions. Hypoxia increased hydrogen peroxide concentrations 300-fold and SA significantly augmented the release of hydrogen peroxide under normoxic, but not under hypoxic conditions. Phosphorylation of the pro-survival kinases akt and erk1/2 was not changed by SA under hypoxic conditions, whereas under normoxia SA reduced phosphorylation of erk1/2 after 2 hours. We conclude that in colon carcinoma cells effects of SA on apoptosis and cellular signaling are dependent on the availability of oxygen. -- Highlights: Black-Right-Pointing-Pointer Effects of salicylic acid on colon carcinoma cells grown under normoxic and hypoxic conditions Black-Right-Pointing-Pointer Salicylic acid increases caspase-3/7 activity and hydrogen peroxide release under normoxia Black-Right-Pointing-Pointer Salicylic acid decreases pro-survival erk-1/2 phosphorylation under normoxia Black-Right-Pointing-Pointer Salicylic acid does

  19. Salicylic acid induces apoptosis in colon carcinoma cells grown in-vitro: Influence of oxygen and salicylic acid concentration

    International Nuclear Information System (INIS)

    Zitta, Karina; Meybohm, Patrick; Bein, Berthold; Huang, Ying; Heinrich, Christin; Scholz, Jens; Steinfath, Markus; Albrecht, Martin

    2012-01-01

    In solid tumors the hypoxic environment can promote tumor progression and resistance to therapy. Recently, acetylsalicylic acid a major component of analgesic drugs and its metabolite salicylic acid (SA) have been shown to reduce the risk of colon cancer, but the mechanisms of action remain still unclear. Here we elucidate the effects of physiologically relevant concentrations of SA on colon carcinoma cells (CaCo-2) grown under normoxic and hypoxic conditions. Western blotting, caspase-3/7 apoptosis assays, MTS cell-proliferation assays, LDH cytotoxicity assays and hydrogen peroxide measurements were performed to investigate the effects of 1 and 10 μM SA on CaCo-2 cells grown under normoxic conditions and cells exposed to hypoxia. Under normoxic conditions, SA did not influence cell proliferation or LDH release of CaCo-2 cells. However, caspase-3/7 activity was significantly increased. Under hypoxia, cell proliferation was reduced and LDH release and caspase-3/7 activities were increased. None of these parameters was altered by the addition of SA under hypoxic conditions. Hypoxia increased hydrogen peroxide concentrations 300-fold and SA significantly augmented the release of hydrogen peroxide under normoxic, but not under hypoxic conditions. Phosphorylation of the pro-survival kinases akt and erk1/2 was not changed by SA under hypoxic conditions, whereas under normoxia SA reduced phosphorylation of erk1/2 after 2 hours. We conclude that in colon carcinoma cells effects of SA on apoptosis and cellular signaling are dependent on the availability of oxygen. -- Highlights: ► Effects of salicylic acid on colon carcinoma cells grown under normoxic and hypoxic conditions ► Salicylic acid increases caspase-3/7 activity and hydrogen peroxide release under normoxia ► Salicylic acid decreases pro-survival erk-1/2 phosphorylation under normoxia ► Salicylic acid does not influence any of the investigated parameters under hypoxia

  20. Deep inelastic singlet structure functions and scaling violation

    Energy Technology Data Exchange (ETDEWEB)

    Wen-zhu, Li; Bing-xun, Hu

    1984-02-01

    The flavour singlet structure functions of deep inelastic scattering processes can yield more decisive tests of QCD than the non-singlet. We give analytical expression for flavour singlet structure functions through analysing the lepton-nucleon deep inelastic scattering processes by means of QCD and using Jacobi polynomials. This expression contains 4 to 5 parameters and shows the changes of the singlet structure functions with x and Q/sup 2/ very well. In QCD leading order, the conclusion is in reasonable agreement with experimental data.

  1. Astrophysical constraints on singlet scalars at LHC

    Science.gov (United States)

    Hertzberg, Mark P.; Masoumi, Ali

    2017-04-01

    We consider the viability of new heavy gauge singlet scalar particles at colliders such as the LHC . Our original motivation for this study came from the possibility of a new heavy particle of mass ~ TeV decaying significantly into two photons at colliders, such as LHC, but our analysis applies more broadly. We show that there are significant constraints from astrophysics and cosmology on the simplest UV complete models that incorporate such new particles and its associated collider signal. The simplest and most obvious UV complete model that incorporates such signals is that it arises from a new singlet scalar (or pseudo-scalar) coupled to a new electrically charged and colored heavy fermion. Here we show that these new fermions (and anti-fermions) would be produced in the early universe, then form new color singlet heavy mesons with light quarks, obtain a non-negligible freeze-out abundance, and remain in kinetic equilibrium until decoupling. These heavy mesons possess interesting phenomenology, dependent on their charge, including forming new bound states with electrons and protons. We show that a significant number of these heavy states would survive for the age of the universe and an appreciable number would eventually be contained within the earth and solar system. We show that this leads to detectable consequences, including the production of highly energetic events from annihilations on earth, new spectral lines, and, spectacularly, the destabilization of stars. The lack of detection of these consequences rules out such simple UV completions, putting pressure on the viability of such new particles at LHC . To incorporate such a scalar would require either much more complicated UV completions or even further new physics that provides a decay channel for the associated fermion.

  2. Astrophysical constraints on singlet scalars at LHC

    Energy Technology Data Exchange (ETDEWEB)

    Hertzberg, Mark P.; Masoumi, Ali, E-mail: mark.hertzberg@tufts.edu, E-mail: ali@cosmos.phy.tufts.edu [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)

    2017-04-01

    We consider the viability of new heavy gauge singlet scalar particles at colliders such as the LHC . Our original motivation for this study came from the possibility of a new heavy particle of mass ∼ TeV decaying significantly into two photons at colliders, such as LHC, but our analysis applies more broadly. We show that there are significant constraints from astrophysics and cosmology on the simplest UV complete models that incorporate such new particles and its associated collider signal. The simplest and most obvious UV complete model that incorporates such signals is that it arises from a new singlet scalar (or pseudo-scalar) coupled to a new electrically charged and colored heavy fermion. Here we show that these new fermions (and anti-fermions) would be produced in the early universe, then form new color singlet heavy mesons with light quarks, obtain a non-negligible freeze-out abundance, and remain in kinetic equilibrium until decoupling. These heavy mesons possess interesting phenomenology, dependent on their charge, including forming new bound states with electrons and protons. We show that a significant number of these heavy states would survive for the age of the universe and an appreciable number would eventually be contained within the earth and solar system. We show that this leads to detectable consequences, including the production of highly energetic events from annihilations on earth, new spectral lines, and, spectacularly, the destabilization of stars. The lack of detection of these consequences rules out such simple UV completions, putting pressure on the viability of such new particles at LHC . To incorporate such a scalar would require either much more complicated UV completions or even further new physics that provides a decay channel for the associated fermion.

  3. Singlet exciton interactions in crystalline naphthalene

    International Nuclear Information System (INIS)

    Heisel, F.; Miehe, J.A.; Sipp, B.

    1978-01-01

    The decay of prompt fluorescence in crystalline naphthalene at 300 K, excited by picosecond 266 nm pulse, has been studied as a function of excitation intensity. Experimental decay curves can be fitted only when the exponential distribution in depth of excitation and the radial (gaussian) intensity profile of the excitation are both taken into account. From analysis of decay at early time ( -10 cm 3 s -1 . If the reaction is diffusion-limited, this rate implies an average singlet diffusivity Dsub(S)=(2+-1)10 -4 cm 2 s -1

  4. Singlet deflected anomaly/gauge mediation

    International Nuclear Information System (INIS)

    Blas, J. de; Delgado, A.

    2012-01-01

    We study an extension of the standard anomaly/gauge mediation scenario where the messenger fields have direct interactions with an extra gauge singlet. This realizes a phenomenologically viable NMSSM-like scenario free of the μ-b μ problem. Current cosmological constraints imply a small size for the anomaly-mediation contributions, unless some source of R-parity violation is permitted. In the latter case the allowed regions in the parameter space can be substantially larger than in the corresponding gauge-mediation scenario.

  5. Intramolecular singlet-singlet energy transfer in antenna-substituted azoalkanes.

    Science.gov (United States)

    Pischel, Uwe; Huang, Fang; Nau, Werner M

    2004-03-01

    Two novel azoalkane bichromophores and related model compounds have been synthesised and photophysically characterised. Dimethylphenylsiloxy (DPSO) or dimethylnaphthylsiloxy (DNSO) serve as aromatic donor groups (antenna) and the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) as the acceptor. The UV spectral window of DBO (250-300 nm) allows selective excitation of the donor. Intramolecular singlet-singlet energy transfer to DBO is highly efficient and proceeds with quantum yields of 0.76 with DPSO and 0.99 with DNSO. The photophysical and spectral properties of the bichromophoric systems suggest that energy transfer occurs through diffusional approach of the donor and acceptor within a van der Waals contact at which the exchange mechanism is presumed to dominate. Furthermore, akin to the behaviour of electron-transfer systems in the Marcus inverted region, a rate of energy transfer 2.5 times slower was observed for the system with the more favourable energetics, i.e. singlet-singlet energy transfer from DPSO proceeded slower than from DNSO, although the process is more exergonic for DPSO (-142 kJ mol(-1) for DPSO versus-67 kJ mol(-1) for DNSO).

  6. Effect of the spatiotemporal variability of rainfall inputs in water quality integrated catchment modelling for dissolved oxygen concentrations

    Science.gov (United States)

    Moreno Ródenas, Antonio Manuel; Cecinati, Francesca; ten Veldhuis, Marie-Claire; Langeveld, Jeroen; Clemens, Francois

    2016-04-01

    Maintaining water quality standards in highly urbanised hydrological catchments is a worldwide challenge. Water management authorities struggle to cope with changing climate and an increase in pollution pressures. Water quality modelling has been used as a decision support tool for investment and regulatory developments. This approach led to the development of integrated catchment models (ICM), which account for the link between the urban/rural hydrology and the in-river pollutant dynamics. In the modelled system, rainfall triggers the drainage systems of urban areas scattered along a river. When flow exceeds the sewer infrastructure capacity, untreated wastewater enters the natural system by combined sewer overflows. This results in a degradation of the river water quality, depending on the magnitude of the emission and river conditions. Thus, being capable of representing these dynamics in the modelling process is key for a correct assessment of the water quality. In many urbanised hydrological systems the distances between draining sewer infrastructures go beyond the de-correlation length of rainfall processes, especially, for convective summer storms. Hence, spatial and temporal scales of selected rainfall inputs are expected to affect water quality dynamics. The objective of this work is to evaluate how the use of rainfall data from different sources and with different space-time characteristics affects modelled output concentrations of dissolved oxygen in a simplified ICM. The study area is located at the Dommel, a relatively small and sensitive river flowing through the city of Eindhoven (The Netherlands). This river stretch receives the discharge of the 750,000 p.e. WWTP of Eindhoven and from over 200 combined sewer overflows scattered along its length. A pseudo-distributed water quality model has been developed in WEST (mikedhi.com); this is a lumped-physically based model that accounts for urban drainage processes, WWTP and river dynamics for several

  7. Effects of Dissolved Oxygen Concentration and Iron Addition on Immediate-early Gene Expression of Magnetospirillum gryphiswaldense MSR-1

    DEFF Research Database (Denmark)

    Zhuang, Shiwen; Anyaogu, Diana Chinyere; Kasama, Takeshi

    2017-01-01

    in cultures at 0.5% O2 compared to those at higher oxygen tensions. Moreover, expression of katG (catalase-peroxidase gene) and feoB2 (ferrous transport protein B2 gene) was reduced markedly by iron addition, regardless of oxygen conditions. The data provides a greater understanding of molecular response...

  8. Major, Trace Element Concentration and Triple-Oxygen Isotope Compositions of G- and I-Type Spherules from the Sør Rondane Mountains, East Antarctica

    Science.gov (United States)

    Soens, B.; Goderis, S.; Greenwood, R. C.; McKibbin, S.; Van Ginneken, M.; Vanhaecke, F.; Debaille, V.; Franchi, I. A.; Claeys, Ph.

    2017-07-01

    We present new major, trace element concentration (LA-ICP-MS) and triple-oxygen isotope (LF-IRMS) data for G- and I-type cosmic spherules. This study suggests that both types of micrometeorites may originate from ordinary chondrite parent bodies.

  9. Radiosensitization of CHO cells by the combination of glutathione depletion and low concentrations of oxygen: The effect of different levels of GSH depletion

    International Nuclear Information System (INIS)

    Clark, E.P.; Epp, E.R.; Zachgo, E.A.; Biaglow, J.E.

    1984-01-01

    Recently, the authors have examined the effect of GSH depletion by BSO on CHO cells equilibrated with oxygen at various concentrations (0.05-4.0%) and irradiated with 50 kVp x-rays. This is of interest because of the uncertain radiosensitizing effect GSH depletion may have on cells equilibrated with low oxygen concentrations. GSH depletion (0.1 mM BSO/24 hrs reduced [GSH] ≅ 10% of control) enhanced the radiosensitizing action of moderate (0.4-4.0%) concentrations of oxygen, i.e., GSH depletion reduced the [O/sub 2/] necessary to achieve an equivalent ER by ≅ 2-3 fold. However, GSH depletion was much more effective as a rediosensitizer when cells were equilibrated with low (<0.4%) concentrations of oxygen, i.e., GSH depletion reduced the [O/sub 2/] necessary to achieve an equivalent ER by 8-10 fold. Furthermore, while the addition of exogenous 5 mM GSH restored the ER to that observed when GSH was not depleted, the intracellular [GSH] was not increased. The results of these studies carried out at different levels of GSH depletion are presented

  10. The concentration of oxygen dissolved in tissues at the time of irradiation as a factor in radiotherapy

    International Nuclear Information System (INIS)

    Gray, L.H.; Conger, A.D.; Ebert, M.; Hornsey, S.; Scott, O.C.A.

    1984-01-01

    The sensitivity of tumour cells to X rays has been shown to be about three times as great when irradiated in a well-oxygenated medium as under anoxic conditions. The manner in which sensitivity depends on oxygen tension closely resembles that found by other workers for plant and insect tissues. The sensitivity of the tumour cells to fast neutron radiation is only slightly affected by oxygen tension. Consideration is given to the supply of oxygen to tissues as a factor in radiotherapy, and it is concluded on the basis of existing knowledge that in certain circumstances the effectiveness of X-ray treatment might be increased if the patient were breathing oxygen at the time of irradiation

  11. HRE-type genes are regulated by growth-related changes in internal oxygen concentrations during the normal development of potato (Solanum tuberosum) tubers.

    Science.gov (United States)

    Licausi, Francesco; Giorgi, Federico Manuel; Schmälzlin, Elmar; Usadel, Björn; Perata, Pierdomenico; van Dongen, Joost Thomas; Geigenberger, Peter

    2011-11-01

    The occurrence of hypoxic conditions in plants not only represents a stress condition but is also associated with the normal development and growth of many organs, leading to adaptive changes in metabolism and growth to prevent internal anoxia. Internal oxygen concentrations decrease inside growing potato tubers, due to their active metabolism and increased resistance to gas diffusion as tubers grow. In the present work, we identified three hypoxia-responsive ERF (StHRE) genes whose expression is regulated by the gradual decrease in oxygen tensions that occur when potato tubers grow larger. Increasing the external oxygen concentration counteracted the modification of StHRE expression during tuber growth, supporting the idea that the actual oxygen levels inside the organs, rather than development itself, are responsible for the regulation of StHRE genes. We identified several sugar metabolism-related genes co-regulated with StHRE genes during tuber development and possibly involved in starch accumulation. All together, our data suggest a possible role for low oxygen in the regulation of sugar metabolism in the potato tuber, similar to what happens in storage tissues during seed development.

  12. Physiologic oxygen concentration enhances the stem-like properties of CD133+ human glioblastoma cells in vitro.

    Science.gov (United States)

    McCord, Amy M; Jamal, Muhammad; Shankavaram, Uma T; Shankavarum, Uma T; Lang, Frederick F; Camphausen, Kevin; Tofilon, Philip J

    2009-04-01

    In vitro investigations of tumor stem-like cells (TSC) isolated from human glioblastoma (GB) surgical specimens have been done primarily at an atmospheric oxygen level of 20%. To determine whether an oxygen level more consistent with in situ conditions affects their stem cell-like characteristics, we compared GB TSCs grown under conditions of 20% and 7% oxygen. Growing CD133(+) cells sorted from three GB neurosphere cultures at 7% O(2) reduced their doubling time and increased the self-renewal potential as reflected by clonogenicity. Furthermore, at 7% oxygen, the cultures exhibited an enhanced capacity to differentiate along both the glial and neuronal pathways. As compared with 20%, growth at 7% oxygen resulted in an increase in the expression levels of the neural stem cell markers CD133 and nestin as well as the stem cell markers Oct4 and Sox2. In addition, whereas hypoxia inducible factor 1alpha was not affected in CD133(+) TSCs grown at 7% O(2), hypoxia-inducible factor 2alpha was expressed at higher levels as compared with 20% oxygen. Gene expression profiles generated by microarray analysis revealed that reducing oxygen level to 7% resulted in the up-regulation and down-regulation of a significant number of genes, with more than 140 being commonly affected among the three CD133(+) cultures. Furthermore, Gene Ontology categories up-regulated at 7% oxygen included those associated with stem cells or GB TSCs. Thus, the data presented indicate that growth at the more physiologically relevant oxygen level of 7% enhances the stem cell-like phenotype of CD133(+) GB cells.

  13. Diurnal dynamics of oxygen and carbon dioxide concentrations in shoots and rhizomes of a perennial in a constructed wetland indicate down-regulation of below ground oxygen consumption

    Czech Academy of Sciences Publication Activity Database

    Fausser, A. C.; Dušek, Jiří; Čížková, Hana; Kazda, M.

    2016-01-01

    Roč. 8, JUL (2016), č. článku plw025. ISSN 2041-2851 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073; GA MŠk(CZ) LM2010007 Institutional support: RVO:86652079 Keywords : typha-latifolia l * internal gas-transport * phragmites-australis * convective throughflow * pressurized ventilation * angustifolia l * ex steud * roots * flow * respiration * Aeration * constructed wetland * in-situ field study * internal carbon dioxide * internal oxygen dynamics * Phragmites australis Subject RIV: EF - Botanics OBOR OECD: Plant sciences, botany Impact factor: 2.238, year: 2016

  14. Stability of singlet and triplet trions in carbon nanotubes

    International Nuclear Information System (INIS)

    Ronnow, Troels F.; Pedersen, Thomas G.; Cornean, Horia D.

    2009-01-01

    We investigate singlet and triplet trion states in semiconducting carbon nanotubes using a one-dimensional model. It is concluded that singlet trion states in bind up to 13.6% stronger than exciton states, and that they lower the optical transition energy with up to 50% of the tight binding band gap energy.

  15. Stability of singlet and triplet trions in carbon nanotubes

    DEFF Research Database (Denmark)

    Rønnow, Troels Frimodt; Pedersen, Thomas Garm; Cornean, Horia

    2009-01-01

    We investigate singlet and triplet trion states in semiconducting carbon nanotubes using a one-dimensional model. It is concluded that singlet trion states in bind up to 13.5% stronger than exciton states, and that they lower the optical transition energy with up to 50% of the tight binding band...

  16. Magnetic excitons in singlet-ground-state ferromagnets

    DEFF Research Database (Denmark)

    Birgeneau, R.J.; Als-Nielsen, Jens Aage; Bucher, E.

    1971-01-01

    The authors report measurements of the dispersion of singlet-triplet magnetic excitons as a function of temperature in the singlet-ground-state ferromagnets fcc Pr and Pr3Tl. Well-defined excitons are observed in both the ferromagnetic and paramagnetic regions, but with energies which are nearly...

  17. Spectral filtering modulation method for estimation of hemoglobin concentration and oxygenation based on a single fluorescence emission spectrum in tissue phantoms.

    Science.gov (United States)

    Liu, Quan; Vo-Dinh, Tuan

    2009-10-01

    Hemoglobin concentration and oxygenation in tissue are important biomarkers that are useful in both research and clinical diagnostics of a wide variety of diseases such as cancer. The authors aim to develop simple ratiometric method based on the spectral filtering modulation (SFM) of fluorescence spectra to estimate the total hemoglobin concentration and oxygenation in tissue using only a single fluorescence emission spectrum, which will eliminate the need of diffuse reflectance measurements and prolonged data processing as required by most current methods, thus enabling rapid clinical measurements. The proposed method consists of two steps. In the first step, the total hemoglobin concentration is determined by comparing a ratio of fluorescence intensities at two emission wavelengths to a calibration curve. The second step is to estimate oxygen saturation by comparing a double ratio that involves three emission wavelengths to another calibration curve that is a function of oxygen saturation for known total hemoglobin concentration. Theoretical derivation shows that the ratio in the first step is linearly proportional to the total hemoglobin concentrations and the double ratio in the second step is related to both total hemoglobin concentration and hemoglobin oxygenation for the chosen fiber-optic probe geometry. Experiments on synthetic fluorescent tissue phantoms, which included hemoglobin with both constant and varying oxygenation as the absorber, polystyrene spheres as scatterers, and flavin adenine dinucleotide as the fluorophore, were carried out to validate the theoretical prediction. Tissue phantom experiments confirm that the ratio in the first step is linearly proportional to the total hemoglobin concentration and the double ratio in the second step is related to both total hemoglobin concentrations and hemoglobin oxygenation. Furthermore, the relations between the two ratios and the total hemoglobin concentration and hemoglobin oxygenation are insensitive

  18. Modeling of Nonlinear Dynamics and Synchronized Oscillations of Microbial Populations, Carbon and Oxygen Concentrations, Induced by Root Exudation in the Rhizosphere

    Science.gov (United States)

    Molz, F. J.; Faybishenko, B.; Jenkins, E. W.

    2012-12-01

    Mass and energy fluxes within the soil-plant-atmosphere continuum are highly coupled and inherently nonlinear. The main focus of this presentation is to demonstrate the results of numerical modeling of a system of 4 coupled, nonlinear ordinary differential equations (ODEs), which are used to describe the long-term, rhizosphere processes of soil microbial dynamics, including the competition between nitrogen-fixing bacteria and those unable to fix nitrogen, along with substrate concentration (nutrient supply) and oxygen concentration. Modeling results demonstrate the synchronized patterns of temporal oscillations of competing microbial populations, which are affected by carbon and oxygen concentrations. The temporal dynamics and amplitude of the root exudation process serve as a driving force for microbial and geochemical phenomena, and lead to the development of the Gompetzian dynamics, synchronized oscillations, and phase-space attractors of microbial populations and carbon and oxygen concentrations. The nonlinear dynamic analysis of time series concentrations from the solution of the ODEs was used to identify several types of phase-space attractors, which appear to be dependent on the parameters of the exudation function and Monod kinetic parameters. This phase space analysis was conducted by means of assessing the global and local embedding dimensions, correlation time, capacity and correlation dimensions, and Lyapunov exponents of the calculated model variables defining the phase space. Such results can be used for planning experimental and theoretical studies of biogeochemical processes in the fields of plant nutrition, phyto- and bio-remediation, and other ecological areas.

  19. Magnetism of singlet - singlet ions interacting with an electron gas: application to PrAl2

    International Nuclear Information System (INIS)

    Palermo, L.

    1986-01-01

    Various magnetic quantities are investigated for a system consisting of singlet-singlet ions interacting with an electron gas. In obtaining the magnetic state equations, the molecular field approximation is used. At T=0, an onset magnetic order condition in function of crystal field and exchange parameters and eletronic density of states at Fermi level is derived. A parametric study of the model is performed numerically. Main results are shown on diagrams. From the experimental data existent in the literature for magnetisation, susceptibility and magnetic specific heat of the PrAl 2 , a fitting with the model predictions is obtained using the following parameters: exchange interaction: 611meV; crystal field parameters: 2,5 meV; band with: 10 eV (of a rectangular density of states with 0,8 el/atom). (author) [pt

  20. Effect of phytoremediation on concentrations of benzene, toluene, naphthalene, and dissolved oxygen in groundwater at a former manufactured gas plant site, Charleston, South Carolina, USA, 1998–2014

    Science.gov (United States)

    Landmeyer, James E.; Effinger, Thomas N.

    2016-01-01

    Concentrations of benzene, toluene, naphthalene, and dissolved oxygen in groundwater at a former manufactured gas plant site near Charleston, South Carolina, USA, have been monitored since the installation of a phytoremediation system of hybrid poplar trees in 1998. Between 2000 and 2014, the concentrations of benzene, toluene, and naphthalene (BT&N) in groundwater in the planted area have decreased. For example, in the monitoring well containing the highest concentrations of BT&N, benzene concentrations decreased from 10,200 µg/L to less than 4000 µg/L, toluene concentrations decreased from 2420 µg/L to less than 20 µg/L, and naphthalene concentrations decreased from 6840 µg/L to less than 3000 µg/L. Concentrations of BT&N in groundwater in all wells were observed to be lower during the summer months relative to the winter months of a particular year during the first few years after installing the phytoremediation system, most likely due to increased transpiration and contaminant uptake by the hybrid poplar trees during the warm summer months; this pathway of uptake by trees was confirmed by the detection of benzene, toluene, and naphthalene in trees during sampling events in 2002, and later in the study in 2012. These data suggest that the phytoremediation system affects the groundwater contaminants on a seasonal basis and, over multiple years, has resulted in a cumulative decrease in dissolved-phase contaminant concentrations in groundwater. The removal of dissolved organic contaminants from the aquifer has resulted in a lower demand on dissolved oxygen supplied by recharge and, as a result, the redox status of the groundwater has changed from anoxic to oxic conditions. This study provides much needed information for water managers and other scientists on the viability of the long-term effectiveness of phytoremediation in decreasing groundwater contaminants and increasing dissolved oxygen at sites contaminated by benzene, toluene, and naphthalene.

  1. Complex singlet extension of the standard model

    International Nuclear Information System (INIS)

    Barger, Vernon; McCaskey, Mathew; Langacker, Paul; Ramsey-Musolf, Michael; Shaughnessy, Gabe

    2009-01-01

    We analyze a simple extension of the standard model (SM) obtained by adding a complex singlet to the scalar sector (cxSM). We show that the cxSM can contain one or two viable cold dark matter candidates and analyze the conditions on the parameters of the scalar potential that yield the observed relic density. When the cxSM potential contains a global U(1) symmetry that is both softly and spontaneously broken, it contains both a viable dark matter candidate and the ingredients necessary for a strong first order electroweak phase transition as needed for electroweak baryogenesis. We also study the implications of the model for discovery of a Higgs boson at the Large Hadron Collider.

  2. Singlet versus Triplet Excited State Mediated Photoinduced Dehalogenation Reactions of Itraconazole in Acetonitrile and Aqueous Solutions.

    Science.gov (United States)

    Zhu, Ruixue; Li, Ming-de; Du, Lili; Phillips, David Lee

    2017-04-06

    Photoinduced dehalogenation of the antifungal drug itraconazole (ITR) in acetonitrile (ACN) and ACN/water mixed solutions was investigated using femtosecond and nanosecond time-resolved transient absorption (fs-TA and ns-TA, respectively) and nanosecond time-resolved resonance Raman spectroscopy (ns-TR 3 ) experiments. An excited resonance energy transfer is found to take place from the 4-phenyl-4,5-dihydro-3H-1,2,4-triazol-3-one part of the molecule to the 1,3-dichlorobenzene part of the molecule when ITR is excited by ultraviolet light. This photoexcitation is followed by a fast carbon-halogen bond cleavage that leads to the generation of radical intermediates via either triplet and/or singlet excited states. It is found that the singlet excited state-mediated carbon-halogen cleavage is the predominant dehalogenation process in ACN solvent, whereas a triplet state-mediated carbon-halogen cleavage prefers to occur in the ACN/water mixed solutions. The singlet-to-triplet energy gap is decreased in the ACN/water mixed solvents and this helps facilitate an intersystem crossing process, and thus, the carbon-halogen bond cleavage happens mostly through an excited triplet state in the aqueous solutions examined. The ns-TA and ns-TR 3 results also provide some evidence that radical intermediates are generated through a homolytic carbon-halogen bond cleavage via predominantly the singlet excited state pathway in ACN but via mainly the triplet state pathway in the aqueous solutions. In strong acidic solutions, protonation at the oxygen and/or nitrogen atoms of the 1,2,4-triazole-3-one group appears to hinder the dehalogenation reactions. This may offer the possibility that the phototoxicity of ITR due to the generation of aryl or halogen radicals can be reduced by protonation of certain moieties in suitably designed ITR halogen-containing derivatives.

  3. 3D modeling of effects of increased oxygenation and activity concentration in tumors treated with radionuclides and antiangiogenic drugs

    Energy Technology Data Exchange (ETDEWEB)

    Lagerloef, Jakob H.; Kindblom, Jon; Bernhardt, Peter [Department of Radiation Physics, Goeteborg University, Goeteborg 41345 (Sweden); Department of Oncology, Sahlgrenska University Hospital, Goeteborg 41345 (Sweden); Department of Radiation Physics, Goeteborg University, Goeteborg, Sweden and Department of Nuclear Medicine, Sahlgrenska University Hospital, Goeteborg 41345 (Sweden)

    2011-08-15

    Purpose: Formation of new blood vessels (angiogenesis) in response to hypoxia is a fundamental event in the process of tumor growth and metastatic dissemination. However, abnormalities in tumor neovasculature often induce increased interstitial pressure (IP) and further reduce oxygenation (pO{sub 2}) of tumor cells. In radiotherapy, well-oxygenated tumors favor treatment. Antiangiogenic drugs may lower IP in the tumor, improving perfusion, pO{sub 2} and drug uptake, by reducing the number of malfunctioning vessels in the tissue. This study aims to create a model for quantifying the effects of altered pO{sub 2}-distribution due to antiangiogenic treatment in combination with radionuclide therapy. Methods: Based on experimental data, describing the effects of antiangiogenic agents on oxygenation of GlioblastomaMultiforme (GBM), a single cell based 3D model, including 10{sup 10} tumor cells, was developed, showing how radionuclide therapy response improves as tumor oxygenation approaches normal tissue levels. The nuclides studied were {sup 90}Y, {sup 131}I, {sup 177}Lu, and {sup 211}At. The absorbed dose levels required for a tumor control probability (TCP) of 0.990 are compared for three different log-normal pO{sub 2}-distributions: {mu}{sub 1} = 2.483, {sigma}{sub 1} = 0.711; {mu}{sub 2} = 2.946, {sigma}{sub 2} = 0.689; {mu}{sub 3} = 3.689, and {sigma}{sub 3} = 0.330. The normal tissue absorbed doses will, in turn, depend on this. These distributions were chosen to represent the expected oxygen levels in an untreated hypoxic tumor, a hypoxic tumor treated with an anti-VEGF agent, and in normal, fully-oxygenated tissue, respectively. The former two are fitted to experimental data. The geometric oxygen distributions are simulated using two different patterns: one Monte Carlo based and one radially increasing, while keeping the log-normal volumetric distributions intact. Oxygen and activity are distributed, according to the same pattern. Results: As tumor pO{sub 2

  4. Effects of Acute Bleeding Followed by Hydroxyethyl Starch 130/0.4 or a Crystalloid on Propofol Concentrations, Cerebral Oxygenation, and Electroencephalographic and Haemodynamic Variables in Pigs

    Directory of Open Access Journals (Sweden)

    Aura Silva

    2014-01-01

    Full Text Available Bleeding changes the haemodynamics, compromising organ perfusion. In this study, the effects of bleeding followed by replacement with hydroxyethyl starch 130/0.4 (HES or lactated Ringer’s (LR on cerebral oxygenation and electroencephalogram-derived parameters were investigated. Twelve young pigs under propofol-remifentanil anaesthesia were bled 30 mL/kg and, after a 20-minute waiting period, volume replacement was performed with HES (GHES; N=6 or LR (GRL; N=6. Bleeding caused a decrease of more than 50% in mean arterial pressure (P<0.01 and a decrease in cerebral oximetry (P=0.039, bispectral index, and electroencephalogram total power (P=0.04 and P<0.01, resp., while propofol plasma concentrations increased (P<0.01. Both solutions restored the haemodynamics and cerebral oxygenation similarly and were accompanied by an increase in electroencephalogram total power. No differences between groups were found. However, one hour after the end of the volume replacement, the cardiac output (P=0.03 and the cerebral oxygenation (P=0.008 decreased in the GLR and were significantly lower than in GHES (P=0.02. Volume replacement with HES 130/0.4 was capable of maintaining the cardiac output and cerebral oxygenation during a longer period than LR and caused a decrease in the propofol plasma concentrations.

  5. On-line determination of glucose and lactate concentrations in animal cell culture based on fibre optic detection of oxygen in flow-injection analysis.

    Science.gov (United States)

    Dremel, B A; Li, S Y; Schmid, R D

    1992-01-01

    A flow-injection analysis (FIA) system based on fibre optic detection of oxygen consumption using immobilized glucose oxidase (GOD) and lactate oxidase (LOD) is described for the on-line monitoring of glucose and lactate concentrations in animal cell cultures. The consumption of oxygen was determined via dynamic quenching by molecular oxygen of the fluorescence of an indicator. GOD and LOD were immobilized on controlled pore glass (CPG) in enzyme reactors which were directly linked to a specially designed fibre optic flow-through cell covering the oxygen optrode. The system is linear for 0-30 mM glucose, with an r.s.d. of 5% at 30 mM (five measurements) and for 0-30 mM lactate, with an r.s.d. of 5% at 30 mM (five measurements). The enzyme reactors used were stable for more than 4 weeks in continuous operation, and it was possible to analyse up to 20 samples per hour. The system has been successfully applied to the on-line monitoring of glucose and lactate concentrations of an animal cell culture designed for the production of recombinant human antithrombine III (AT-III). Results of the on-line measurement obtained by the FIA system were compared with the off-line results obtained by a glucose and lactate analyser from Yellow Springs Instrument Company (YSI).

  6. The electroweak phase transition in models with gauge singlets

    International Nuclear Information System (INIS)

    Ahriche, A.

    2007-01-01

    A strong first order phase transition is needed for generating the baryon asymmetry; and also to save it during the electroweak phase transition (EWPT). However this condition is not fulfilled within the Standard Model (SM), but in its extensions. It is widely believed that the existence of singlet scalars in some Standard Model extensions can easily make the EWPT strongly first order. In this work, we will examine the strength of the EWPT in the simplest extension of the SM with a real gauge singlet using the sphaleron energy at the critical temperature. We find that the phase transition is stronger by adding a singlet; and also that the criterion for a strong phase transition Ω(T c )/T c >or similar 1, where Ω = (v 2 + (x - x 0 ) 2 ) ( 1)/(2) and x(x 0 ) is the singlet vacuum expectation value in the broken (symmetric) phase, is not valid for models containing singlets, even though often used in the literature. The usual condition v c /T c >or similar 1 is more meaningful, and it is satisfied for the major part of the parameter space for physically allowed Higgs masses. Then it is convenient to study the EWPT in models with singlets that couple only to the Higgs doublets, by replacing the singlets by their vevs. (orig.)

  7. The electroweak phase transition in models with gauge singlets

    Energy Technology Data Exchange (ETDEWEB)

    Ahriche, A.

    2007-04-18

    A strong first order phase transition is needed for generating the baryon asymmetry; and also to save it during the electroweak phase transition (EWPT). However this condition is not fulfilled within the Standard Model (SM), but in its extensions. It is widely believed that the existence of singlet scalars in some Standard Model extensions can easily make the EWPT strongly first order. In this work, we will examine the strength of the EWPT in the simplest extension of the SM with a real gauge singlet using the sphaleron energy at the critical temperature. We find that the phase transition is stronger by adding a singlet; and also that the criterion for a strong phase transition {omega}(T{sub c})/T{sub c} >or similar 1, where {omega} = (v{sup 2} + (x - x{sub 0}){sup 2}){sup (}1)/(2) and x(x{sub 0}) is the singlet vacuum expectation value in the broken (symmetric) phase, is not valid for models containing singlets, even though often used in the literature. The usual condition v{sub c}/T{sub c} >or similar 1 is more meaningful, and it is satisfied for the major part of the parameter space for physically allowed Higgs masses. Then it is convenient to study the EWPT in models with singlets that couple only to the Higgs doublets, by replacing the singlets by their vevs. (orig.)

  8. Differential concentration-specific effects of caffeine on cell viability, oxidative stress, and cell cycle in pulmonary oxygen toxicity in vitro

    International Nuclear Information System (INIS)

    Tiwari, Kirti Kumar; Chu, Chun; Couroucli, Xanthi; Moorthy, Bhagavatula; Lingappan, Krithika

    2014-01-01

    Highlights: • Caffeine at 0.05 mM decreases oxidative stress in hyperoxia. • Caffeine at 1 mM decreases cell viability, increases oxidative stress in hyperoxia. • Caffeine at 1 but not 0.05 mM, abrogates hyperoxia-induced G2/M arrest. - Abstract: Caffeine is used to prevent bronchopulmonary dysplasia (BPD) in premature neonates. Hyperoxia contributes to the development of BPD, inhibits cell proliferation and decreases cell survival. The mechanisms responsible for the protective effect of caffeine in pulmonary oxygen toxicity remain largely unknown. A549 and MLE 12 pulmonary epithelial cells were exposed to hyperoxia or maintained in room air, in the presence of different concentrations (0, 0.05, 0.1 and 1 mM) of caffeine. Caffeine had a differential concentration-specific effect on cell cycle progression, oxidative stress and viability, with 1 mM concentration being deleterious and 0.05 mM being protective. Reactive oxygen species (ROS) generation during hyperoxia was modulated by caffeine in a similar concentration-specific manner. Caffeine at 1 mM, but not at the 0.05 mM concentration decreased the G2 arrest in these cells. Taken together this study shows the novel funding that caffeine has a concentration-specific effect on cell cycle regulation, ROS generation, and cell survival in hyperoxic conditions

  9. Differential concentration-specific effects of caffeine on cell viability, oxidative stress, and cell cycle in pulmonary oxygen toxicity in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Tiwari, Kirti Kumar; Chu, Chun; Couroucli, Xanthi; Moorthy, Bhagavatula; Lingappan, Krithika, E-mail: lingappa@bcm.edu

    2014-08-08

    Highlights: • Caffeine at 0.05 mM decreases oxidative stress in hyperoxia. • Caffeine at 1 mM decreases cell viability, increases oxidative stress in hyperoxia. • Caffeine at 1 but not 0.05 mM, abrogates hyperoxia-induced G2/M arrest. - Abstract: Caffeine is used to prevent bronchopulmonary dysplasia (BPD) in premature neonates. Hyperoxia contributes to the development of BPD, inhibits cell proliferation and decreases cell survival. The mechanisms responsible for the protective effect of caffeine in pulmonary oxygen toxicity remain largely unknown. A549 and MLE 12 pulmonary epithelial cells were exposed to hyperoxia or maintained in room air, in the presence of different concentrations (0, 0.05, 0.1 and 1 mM) of caffeine. Caffeine had a differential concentration-specific effect on cell cycle progression, oxidative stress and viability, with 1 mM concentration being deleterious and 0.05 mM being protective. Reactive oxygen species (ROS) generation during hyperoxia was modulated by caffeine in a similar concentration-specific manner. Caffeine at 1 mM, but not at the 0.05 mM concentration decreased the G2 arrest in these cells. Taken together this study shows the novel funding that caffeine has a concentration-specific effect on cell cycle regulation, ROS generation, and cell survival in hyperoxic conditions.

  10. Suppression of aqueous corrosion of La(Fe0.88Si0.12)13 by reducing dissolved oxygen concentration for high-performance magnetic refrigeration

    International Nuclear Information System (INIS)

    Fujieda, S.; Fukamichi, K.; Suzuki, S.

    2014-01-01

    Highlights: • The aqueous corrosion of La(Fe 0.88 Si 0.12 ) 13 and its suppression were investigated. • The lattice expansion after immersion was caused by the hydrogen absorption. • The itinerant-electron metamagnetic transition became indistinct after immersion. • The aqueous corrosion was suppressed by reducing the dissolved oxygen concentration. - Abstract: The itinerant-electron metamagnetic transition of La(Fe 0.88 Si 0.12 ) 13 becomes indistinct after immersion in distilled-water containing about 8 ppm of the dissolved oxygen (DO) concentration because of aqueous corrosion. However, the aqueous corrosion of La(Fe 0.88 Si 0.12 ) 13 is significantly suppressed by reducing the DO concentration. Thus, isothermal magnetic entropy change after immersion for 30 days in deaerated distilled-water with a DO concentration less than 0.1 ppm is larger than that after immersion for 5 days in distilled-water containing about 8 ppm of the DO concentration. Consequently, the reduction of the DO concentration is effective for preservation of the excellent magnetocaloric effects of La(Fe 0.88 Si 0.12 ) 13 in an aqueous solution, which is a promising heat transfer fluid of room-temperature magnetic refrigeration

  11. Effect of hyperbaric oxygen therapy on whole blood cyanide concentrations in carbon monoxide intoxicated patients from fire accidents

    DEFF Research Database (Denmark)

    Lawson-Smith, Pia; Jansen, Erik C; Hilsted, Linda

    2010-01-01

    Hydrogen cyanide (HCN) and carbon monoxide (CO) may be important components of smoke from fire accidents. Accordingly, patients admitted to hospital from fire accidents may have been exposed to both HCN and CO. Cyanide (CN) intoxication results in cytotoxic hypoxia leading to organ dysfunction...... and possibly death. While several reports support the use of hyperbaric oxygen therapy (HBO) for the treatment of severe CO poisoning, limited data exist on the effect of HBO during CN poisoning. HBO increases the elimination rate of CO haemoglobin in proportion to the increased oxygen partial pressure...

  12. Singlet Extensions of the MSSM with ℤ4R Symmetry

    International Nuclear Information System (INIS)

    Ratz, Michael; Vaudrevange, Patrick K. S.

    2015-01-01

    We discuss singlet extensions of the MSSM with ℤ 4 R symmetry. We show that holomorphic zeros can avoid a potentially large coefficient of the term linear in the singlet. The emerging model has both an effective μ term and a supersymmetric mass term for the singlet μ N which are controlled by the gravitino mass. The μ term turns out to be suppressed against μ N by about one or two orders of magnitude. We argue that this class of models might provide us with a solution to the little hierarchy problem of the MSSM

  13. Quantitative determination of localized tissue oxygen concentration in vivo by two-photon excitation phosphorescence lifetime measurements

    NARCIS (Netherlands)

    Mik, Egbert G.; van Leeuwen, Ton G.; Raat, Nicolaas J.; Ince, Can

    2004-01-01

    This study describes the use of two-photon excitation phosphorescence lifetime measurements for quantitative oxygen determination in vivo. Doubling the excitation wavelength of Pd-porphyrin from visible light to the infrared allows for deeper tissue penetration and a more precise and confined

  14. Photochemical Dynamics of Intramolecular Singlet Fission

    Science.gov (United States)

    Lin, Zhou; Iwasaki, Hikari; Van Voorhis, Troy

    2017-06-01

    Singlet fission (SF) converts a singlet exciton (S_1) into a pair of triplet ones (T_1) via a ``multi-exciton'' (ME) intermediate: S_1 \\longleftrightarrow ^1ME \\longleftrightarrow ^1(T_1T_1) \\longrightarrow 2T_1. In exothermic cases, e.g., crystalline pentacene or its derivatives, the quantum yield of SF can reach 200%. With SF doubling the electric current generated by an incident high-energy photon, the solar conversion efficiency in pentacene-based organic photovoltaics (OPVs) can exceed the Shockley-Queisser limit of 33.7%. The ME state is popularly considered to be a dimeric state with significant charge transfer (CT) character that is strongly coupled to both S_1 and ^1(T_1T_1), while this local model lacks strong support from full quantum dynamics studies. Intramolecular SF (ISF) occurring to covalently-bound dimers in the solution phase is an excellent model for a straightforward dynamics simulation of local excitons. In the present study, we investigate the ISF mechanisms for three covalently-bound dimers of pentacene derivatives, including ortho-, meta-, and para-bis(6,13-bis(triisopropylsilylethynyl)pentacene)benzene, in non-protic solvents. Specifically, we propagate the real-time, non-adiabatic quantum mechanical/molecular mechanical (QM/MM) dynamics on the potential energy surfaces associated with the states of S_1, ^1(T_1T_1) and CT. We explore how the energies of these ISF-relevant states and the non-adiabatic couplings between each other fluctuate with time and the instantaneous molecular configuration (e.g., intermonomer distance and orientation). We also quantitatively compare Condon and non-Condon ISF dynamics with solution-phase spectroscopic data. Our results allow us to understand the roles of CT energy levels in the ISF mechanism and propose a design strategy to maximize ISF efficiency. M. B. Smith and J. Michl, Chem. Rev. 110, 6891 (2010). W. Shockley and H. J. Queisser, J. Appl. Phys. 32, 510 (1961). T. C. Berkelbach, M. S. Hybertsen

  15. Hyperpolarized singlet NMR on a small animal imaging system

    DEFF Research Database (Denmark)

    Laustsen, Christoffer; Pileio, Giuseppe; Tayler, Michael C. D.

    2012-01-01

    Nuclear spin hyperpolarization makes a significant advance toward overcoming the sensitivity limitations of in vivo magnetic resonance imaging, particularly in the case of low-gamma nuclei. The sensitivity may be improved further by storing the hyperpolarization in slowly relaxing singlet...... populations of spin- 1/2 pairs. Here, we report hyperpolarized 13C spin order transferred into and retrieved from singlet spin order using a small animal magnetic resonance imaging scanner. For spins in sites with very similar chemical shifts, singlet spin order is sustained in high magnetic field without...... requiring strong radiofrequency irradiation. The demonstration of robust singlet-to-magnetization conversion, and vice versa, on a small animal scanner, is promising for future in vivo and clinical deployments....

  16. Microscopic theory of singlet exciton fission. III. Crystalline pentacene

    International Nuclear Information System (INIS)

    Berkelbach, Timothy C.; Reichman, David R.; Hybertsen, Mark S.

    2014-01-01

    We extend our previous work on singlet exciton fission in isolated dimers to the case of crystalline materials, focusing on pentacene as a canonical and concrete example. We discuss the proper interpretation of the character of low-lying excited states of relevance to singlet fission. In particular, we consider a variety of metrics for measuring charge-transfer character, conclusively demonstrating significant charge-transfer character in the low-lying excited states. The impact of this electronic structure on the subsequent singlet fission dynamics is assessed by performing real-time master-equation calculations involving hundreds of quantum states. We make direct comparisons with experimental absorption spectra and singlet fission rates, finding good quantitative agreement in both cases, and we discuss the mechanistic distinctions that exist between small isolated aggregates and bulk systems

  17. Microscopic theory of singlet exciton fission. III. Crystalline pentacene

    Energy Technology Data Exchange (ETDEWEB)

    Berkelbach, Timothy C., E-mail: tcb2112@columbia.edu; Reichman, David R., E-mail: drr2103@columbia.edu [Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 (United States); Hybertsen, Mark S., E-mail: mhyberts@bnl.gov [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

    2014-08-21

    We extend our previous work on singlet exciton fission in isolated dimers to the case of crystalline materials, focusing on pentacene as a canonical and concrete example. We discuss the proper interpretation of the character of low-lying excited states of relevance to singlet fission. In particular, we consider a variety of metrics for measuring charge-transfer character, conclusively demonstrating significant charge-transfer character in the low-lying excited states. The impact of this electronic structure on the subsequent singlet fission dynamics is assessed by performing real-time master-equation calculations involving hundreds of quantum states. We make direct comparisons with experimental absorption spectra and singlet fission rates, finding good quantitative agreement in both cases, and we discuss the mechanistic distinctions that exist between small isolated aggregates and bulk systems.

  18. Comparison of NO titration and fiber optics catalytic probes for determination of neutral oxygen atom concentration in plasmas and postglows

    International Nuclear Information System (INIS)

    Mozetic, Miran; Ricard, Andre; Babic, Dusan; Poberaj, Igor; Levaton, Jacque; Monna, Virginie; Cvelbar, Uros

    2003-01-01

    A comparative study of two different absolute methods NO titration and fiber optics catalytic probe (FOCP) for determination of neutral oxygen atom density is presented. Both methods were simultaneously applied for measurements of O density in a postglow of an Ar/O 2 plasma created by a surfatron microwave generator with the frequency of 2.45 GHz an adjustable output power between 30 and 160 W. It was found that the two methods gave similar results. The advantages of FOCP were found to be as follows: it is a nondestructive method, it enables real time measuring of the O density, it does not require any toxic gas, and it is much faster than NO titration. The advantage of NO titration was found to be the ability to measure O density in a large range of dissociation of oxygen molecules

  19. 2HDM portal for Singlet-Doublet Dark Matter

    OpenAIRE

    Arcadi, Giorgio

    2018-01-01

    We present an extensive analysis of a model in which the (Majorana) Dark Matter candidate is a mixture between a SU(2) singlet and two SU(2) doublets. This kind of setup takes the name of singlet-doublet model. We will investigate in detail an extension of this model in which the Dark Matter sector interactions with a 2-doublet Higgs sector enforcing the complementarity between Dark Matter phenomenology and searches of extra Higgs bosons.

  20. Singlet Fission in Rubrene Derivatives: Impact of Molecular Packing

    KAUST Repository

    Sutton, Christopher

    2017-03-13

    We examine the properties of six recently synthesized rubrene derivatives (with substitutions on the side phenyl rings) that show vastly different crystal structures. In order to understand how packing in the solid state affects the excited states and couplings relevant for singlet fission, the lowest excited singlet (S), triplet (T), multiexciton (TT), and charge-transfer (CT) states of the rubrene derivatives are compared to known singlet fission materials [tetracene, pentacene, 5,12-diphenyltetracene (DPT), and rubrene itself]. While a small difference of less than 0.2 eV is calculated for the S and TT energies, a range of 0.50 to 1.2 eV in the CT energies and nearly 3 orders of magnitude in the electronic couplings are computed for the rubrene derivatives in their crystalline packings, which strongly affects the role of the CT state in facilitating SF. To rationalize experimental observations of singlet fission occurring in amorphous phases of rubrene, DPT, and tetracene, we use molecular dynamics (MD) simulations to assess the impact of molecular packing and orientations and to gain a better understanding of the parameters that control singlet fission in amorphous films compared to crystalline packings. The MD simulations point to a crystalline-like packing for thin films of tetracene; on the other hand, DPT, rubrene, and the rubrene derivatives all show various degrees of disorder with a number of sites that have larger electronic couplings than in the crystal, which can facilitate singlet fission in such thin films. Our analysis underlines the potential of these materials as promising candidates for singlet fission and helps understand how various structural motifs affect the critical parameters that control the ability of a system to undergo singlet fission.

  1. Inhaled nitric oxide and high concentrations of oxygen in pediatrics patients with congenital cardiopathy and pulmonary hypertension: report of five cases

    Directory of Open Access Journals (Sweden)

    Werther Brunow de Carvalho

    Full Text Available Five patients with ages ranging from 6 months to 3 years were analyzed. All received inhaled nitric oxide (NO - 20 parts per million (ppm and oxygen (0(2 - at a concentration of 90-95% by means of an oxygen hood. Mean Pulmonary Artery Pressure (MPAP, Mean Aortic Pressure (MAoP, Pulmonary Vascular Resistance (PVR and Systemic Vascular Resistance (SVR were measured and the calculation of their relationship to pulmonary/systemic flow (Qp/Qs was performed by the catheterization' of the femoral artery vein. Three patients presented reduction in PVR and increase in Qp/Qs. There were no systemic alterations or any side effect from using NO.

  2. The concentration of optimum dissolved oxygen levels for growth of mangrove crab Scylla serrata seed in recirculation system

    Directory of Open Access Journals (Sweden)

    Kurnia Faturrohman

    2017-07-01

    Full Text Available ABSTRACT This study aimed to determine optimum dissolved oxygen (DO through the addition of aeration and to evaluate the role of dissolved oxygen on production performance and stress responses of mangrove crab Scylla serrata. Experimental design used was complete randomized design with four treatments namely no aeration (A, one point aeration (B, two points aeration (C, and three points aeration (D. All treatments replicated three times. The crab with the average of body weight 45.6±2.1 g/individual cultured in a plastic box (40×30×30 cm3. The stocking densities was 10 crab/box. Crab was cultured within 42 days and were fed two times a day by restricted method (15% of the total biomass. The result showed that C treatment produced 5.51 mg/L dissolved oxygen and gave the best result of mangrove crabs production performance  with 60% survival, 0.83±0.03 g/day absolute growth rate and food conversion ratio 1.1. It also showed good response to the stress that indicated by the cortisol level (10.159 µg/dL. The best results of coefficient of diversity showed by D treatment that was 13.5%. The water quality during study period was fluctuative as affected by different dissolved oxygen value. Keyword: mangrove crabs, dissolved oxygen, production performance  ABSTRAK Penelitian ini bertujuan menentukan kadar oksigen terlarut (OT atau dissolved oxygen (DO yang optimum melalui penentuan titik aerasi serta mengevalusi peranan oksigen terlarut terhadap kinerja produksi dan respons stres kepiting bakau Scylla serrata. Rancangan penelitian yang digunakan adalah rancangan acak lengkap dengan empat pelakuan (penambahan titik aerasi dengan rincian A, tidak menggunakan titik aerasi; B, satu titik aerasi; C, dua titik aerasi dan D, tiga titik aerasi dan tiga ulangan. Kepiting bakau yang digunakan memiliki berat rata-rata 45,6±2,1 g/ekor dengan padat tebar 10 ekor/wadah. Wadah yang digunakan selama pemeliharaan adalah bak fiber plastik yang berukuran 40

  3. The effect of oxygen exposure on pentacene electronic structure

    NARCIS (Netherlands)

    Vollmer, A; Jurchescu, OD; Arfaoui, [No Value; Salzmann, [No Value; Palstra, TTM; Rudolf, P; Niemax, J; Pflaum, J; Rabe, JP; Koch, N; Arfaoui, I.; Salzmann, I.

    We use ultraviolet photoelectron spectroscopy to investigate the effect of oxygen and air exposure on the electronic structure of pentacene single crystals and thin films. it is found that O-2 and water do not react noticeably with pentacene, whereas singlet oxygen/ozone readily oxidize the organic

  4. Selective oxidation of glycerol to formic acid in highly concentrated aqueous solutions with molecular oxygen using V-substituted phosphomolybdic acids

    KAUST Repository

    Zhang, Jizhe

    2014-01-01

    Formic acid is an important commodity chemical as well as a promising medium for hydrogen storage and hydrogen production. In this paper, we report that formic acid can be produced through selective oxidation of glycerol, a low-cost by-product of biodiesel, by using vanadium-substituted phosphomolybdic acids as catalysts and molecular oxygen as the oxidant. Significantly, this catalytic system allows for high-concentration conversions and thus leads to exceptional efficiency. Specifically, 3.64 g of formic acid was produced from 10 g of glycerol/water (50/50 in weight) solution. © 2014 the Partner Organisations.

  5. Effects of dissolved oxygen concentration on photosynthetic bacteria wastewater treatment: Pollutants removal, cell growth and pigments production.

    Science.gov (United States)

    Meng, Fan; Yang, Anqi; Zhang, Guangming; Wang, Hangyao

    2017-10-01

    Dissolved oxygen (DO) is an important parameter in photosynthetic bacteria (PSB) wastewater treatment. This study set different DO levels and detected the pollutants removal, PSB growth and pigments production. Results showed that DO significantly influenced the performances of PSB wastewater treatment process. The highest COD (93%) and NH 3 -N removal (83%) was achieved under DO of 4-8mg/L, but DO of 2-4mg/L was recommended considering the aeration cost. PSB biomass reached 1645mg/L under DO of 4-8mg/L with satisfying co-enzyme Q10 content. The biomass yield was relatively stable at all DO levels. For bacteriochlorophyll and carotenoids, DO>1mg/L could satisfy their production. On the other hand, DOpigments production occurred at 24h; biomass reached peak at 48h; and the optimal time for pollutants removal was 72h. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Induced ferromagnetic and gas sensing properties in ZnO-nanostructures by altering defect concentration of oxygen and zinc vacancies

    CSIR Research Space (South Africa)

    Motaung, DE

    2015-01-01

    Full Text Available synthesis reaction-time due to a decreased surface area, as well as VþO and VZn concentrations. Thus, the synthesis reaction-time clearly controls the relative occupancy of the VþO and VZn present on the surface of ZnO- nanostructures, which is enunciated...

  7. Quantitative relations between chemical oxygen demand concentration and its influence factors in the sluice-controlled river reaches of Shaying River, China.

    Science.gov (United States)

    Dou, Ming; Li, Guiqiu; Li, Congying

    2015-01-01

    Recent research on the effects of dam and sluice construction on the water environment has attracted extensive attention from academia and governments alike. Because the operation of sluices greatly alters environmental factors such as water flow and sediment load, the water quality in sluice-controlled river reaches (SCRRs) undergoes complex changes compared with those in normal reaches. This work used river reaches near the Huaidian Sluice in Shaying River of China as a case study to analyse the effects of sluice operation on water quality evolution in SCRRs. The most influential factors affecting the rate of change in chemical oxygen demand (COD) concentration in SCRRs were identified through water quality monitoring experiments performed under various modes of sluice operation and by applying a statistical method 'partial correlation analysis'. Then, a hydrodynamic model incorporating sluice operation and a water quality transport and transform model incorporating the release of endogenous loads were developed. Using these two models, the processes of temporal and spatial change of COD concentrations in the SCRRs were simulated under various scenarios designed to represent the dominant factors of influence. Finally, the simulation results were used to develop empirical relationships between the rate of change in COD concentrations and the dominant factors of influence. The results reveal that three factors, i.e., water inflow concentration, gate opening size, and gate opening number, are the dominant factors of influence, and there are logarithmic relationships between the rate of change in COD concentration in the SCRRs and these factors.

  8. Element Distribution in the Oxygen-Rich Side-Blow Bath Smelting of a Low-Grade Bismuth-Lead Concentrate

    Science.gov (United States)

    Yang, Tianzu; Xiao, Hui; Chen, Lin; Chen, Wei; Liu, Weifeng; Zhang, Duchao

    2018-03-01

    Oxygen-rich side-blow bath smelting (OSBS) technology offers an efficient method for processing complex bismuth-lead concentrates; however, the element distributions in the process remain unclear. This work determined the distributions of elements, i.e., bismuth, lead, silver, copper, arsenic and antimony, in an industrial-scale OSBS process. The feed, oxidized slag and final products were collected from the respective sampling points and analyzed. For the oxidative smelting process, 65% of bismuth and 76% of silver in the concentrate report to the metal alloy, whereas less lead reports to the metal ( 31%) than the oxidized slag ( 44%). Approximately 50% of copper enters the matte, while more than 63% of arsenic and antimony report to the slag. For the reductive smelting process, less than 4.5% of bismuth, lead, silver and copper in the oxidized slag enter the reduced slag, indicating high recoveries of these metal values.

  9. Impact of upwelling events on the sea water carbonate chemistry and dissolved oxygen concentration in the Gulf of Papagayo (Culebra Bay, Costa Rica: Implications for coral reefs

    Directory of Open Access Journals (Sweden)

    Tim Rixen

    2012-04-01

    Full Text Available The Gulf of Papagayo, Pacific coast of Costa Rica, is one of the three seasonal upwelling areas of Mesoamerica. In April 2009, a 29-hour experiment was carried out at the pier of the Marina Papagayo, Culebra Bay. We determined sea surface temperature (SST, dissolved oxygen concentration, salinity, pH, and the partial pressure of CO2 (pCO2. The aragonite saturation state (Ωa as well as the other parameters of the marine carbonate system such as the total dissolved inorganic carbon (DIC and the total alkalinity (TA were calculated based on the measured pH and the pCO2. The entrainment of subsurface waters raised the pCO2 up to 645 µatm. SSTs, dissolved oxygen concentrations decreased form 26.4 to 23.7°C and from 228 to 144 µmol l-1. Ωa dropped down to values of 2.1. Although these changes are assumed to reduce the coral growth, the main reef building coral species within the region (Pocillopora spp. and Pavona clavus reveal growth rates exceeding those measured at other sites in the eastern tropical Pacific. This implies that the negative impact of upwelling on coral growth might be overcompensated by an enhanced energy supply caused by the high density of food and nutrients and more favorable condition for coral growth during the non-upwelling season.

  10. Effect of Serum and Oxygen Concentration on Gene Expression and Secretion of Paracrine Factors by Mesenchymal Stem Cells

    Directory of Open Access Journals (Sweden)

    Patrick Page

    2014-01-01

    Full Text Available Mesenchymal stem cells (MSC secrete paracrine factors that may exert a protective effect on the heart after coronary artery occlusion. This study was done to determine the effect of hypoxia and serum levels on the mRNA expression and secretion of paracrine factors. Mouse bone marrow MSC were cultured with 5% or 20% serum and in either normoxic (21% O2 or hypoxic (1% O2 conditions. Expression of mRNA for vascular endothelial growth factor (VEGF, monocyte chemotactic protein-1 (MCP-1, macrophage inflammatory protein-1α (MIP-1α, MIP-1β, and matrix metalloproteinase-2 (MMP-2 was determined by RT-qPCR. Secretion into the culture media was determined by ELISA. Hypoxia caused a reduction in gene expression for MCP-1 and an increase for VEGF (5% serum, MIP-1α, MIP-1β, and MMP-2. Serum reduction lowered gene expression for VEGF (normoxia, MCP-1 (hypoxia, MIP-1α (hypoxia, MIP-1β (hypoxia, and MMP-2 (hypoxia and increased gene expression for MMP-2 (normoxia. The level of secretion of these factors into the media generally paralleled gene expression with some exceptions. These data demonstrate that serum and oxygen levels have a significant effect on the gene expression and secretion of paracrine factors by MSC which will affect how MSC interact in vivo during myocardial ischemia.

  11. Expression of T helper cell-associated inflammatory mediator mRNAs in cells of bronchoalveolar lavage fluid samples and oxygen concentration in arterial blood samples from healthy horses exposed to hyperbaric oxygen.

    Science.gov (United States)

    Looijen, Maty G P; New, Dallas J; Fischer, Carrie D; Dardari, Rkia; Irwin, Karyn M; Berezowski, Christopher J; Bond, Stephanie L; Léguillette, Renaud

    2016-10-01

    OBJECTIVE To evaluate the mRNA expression of T helper (Th)1, Th2, and Th17 cell-associated inflammatory mediators in cells of bronchoalveolar lavage fluid samples collected from healthy horses exposed to hyperbaric oxygen (HBO) and to monitor blood oxygen concentration during and following HBO therapy. ANIMALS 8 healthy horses. PROCEDURES In a randomized controlled crossover design study, each horse was exposed (beginning day 1) to 100% oxygen at a maximum of 3 atmospheres absolute (304 kPa) daily for 10 days or ambient air at atmospheric pressure in the HBO chamber for an equivalent amount of time (control). Bronchoalveolar lavage fluid samples were collected on days 0 and 10. After validation of candidate reference genes, relative mRNA expressions of various innate inflammatory, Th1 cell-derived, Th2 cell-derived (including eotaxin-2), Th17 cell-derived, and regulatory cytokines were measured by quantitative PCR assays. For 3 horses, arterial blood samples were collected for blood gas analysis during a separate HBO session. RESULTS The optimal combination of reference genes was glyceraldehyde-3-phosphate dehydrogenase, hypoxanthine ribosyltransferase, and ribosomal protein L32. Compared with day 0 findings, expression of eotaxin-2 mRNA was significantly lower (0.12-fold reduction) and the percentage of neutrophils in bronchoalveolar lavage fluid samples was significantly lower on day 10 when horses received HBO therapy. Values of Pao2 rapidly increased (> 800 mm Hg) but immediately decreased to pretreatment values when HBO sessions ended. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that HBO therapy does not increase mRNA expression of inflammatory cytokines, but reduces eotaxin-2 mRNA transcription. The Pao2 increase was transient with no cumulative effects of HBO.

  12. Oxygen diffusion in bilayer polymer films

    DEFF Research Database (Denmark)

    Poulsen, Lars; Zebger, Ingo; Tofte, Jannik Pentti

    2004-01-01

    Experiments to quantify oxygen diffusion have been performed on polymer samples in which a film of poly(ethylene-co-norbornene) was cast onto a film of polystyrene which, in turn, was cast onto an oxygen-impermeable substrate. In the technique employed, the time evolution of oxygen transport...... through the film of poly(ethylene-co-norbornene) and into the polystyrene film was monitored using the phosphorescence of singlet oxygen as a spectroscopic probe. To analyze the data, it was necessary to solve Fick's second law of diffusion for both polymer films. Tractable analytical and numerical...

  13. Effect of hyperbaric oxygen therapy on whole blood cyanide concentrations in carbon monoxide intoxicated patients from fire accidents

    DEFF Research Database (Denmark)

    Lawson-Smith, Pia; Jansen, Erik C; Hilsted, Linda

    2010-01-01

    Hydrogen cyanide (HCN) and carbon monoxide (CO) may be important components of smoke from fire accidents. Accordingly, patients admitted to hospital from fire accidents may have been exposed to both HCN and CO. Cyanide (CN) intoxication results in cytotoxic hypoxia leading to organ dysfunction...... and animal experiments have shown that in rats exposed to CN intoxication, HBO can increase the concentration of CN in whole blood....

  14. Singlet fission efficiency in tetracene-based organic solar cells

    International Nuclear Information System (INIS)

    Wu, Tony C.; Thompson, Nicholas J.; Congreve, Daniel N.; Hontz, Eric; Yost, Shane R.; Van Voorhis, Troy; Baldo, Marc A.

    2014-01-01

    Singlet exciton fission splits one singlet exciton into two triplet excitons. Using a joint analysis of photocurrent and fluorescence modulation under a magnetic field, we determine that the triplet yield within optimized tetracene organic photovoltaic devices is 153% ± 5% for a tetracene film thickness of 20 nm. The corresponding internal quantum efficiency is 127% ± 18%. These results are used to prove the effectiveness of a simplified triplet yield measurement that relies only on the magnetic field modulation of fluorescence. Despite its relatively slow rate of singlet fission, the measured triplet yields confirm that tetracene is presently the best candidate for use with silicon solar cells

  15. Singlet channel coupling in deuteron elastic scattering at intermediate energies

    International Nuclear Information System (INIS)

    Al-Khalili, J.S.; Tostevin, J.A.; Johnson, R.C.

    1990-01-01

    Intermediate energy deuteron elastic scattering is investigated in a three-body model incorporating relativistic kinematics. The effects of deuteron breakup to singlet spin intermediate states, on the elastic scattering observables for the 58 Ni(d vector, d) 58 Ni reaction at 400 and 700 MeV, are studied quantitatively. The singlet-breakup contributions to the elastic amplitude are estimated within an approximate two-step calculation. The calculation makes an adiabatic approximation in the intermediate states propagator which allows the use of closure over the np intermediate states continuum. The singlet channel coupling is found to produce large effects on the calculated reaction tensor analysing power A yy , characteristic of a dynamically induced second-rank tensor interaction. By inspection of the calculated breakup amplitudes we show this induced interaction to be of the T L tensor type. (orig.)

  16. Antioxidant response of the hard shelled mussel Mytilus coruscus exposed to reduced pH and oxygen concentration.

    Science.gov (United States)

    Sui, Yanming; Hu, Menghong; Shang, Yueyong; Wu, Fangli; Huang, Xizhi; Dupont, Sam; Storch, Daniela; Pörtner, Hans-Otto; Li, Jiale; Lu, Weiqun; Wang, Youji

    2017-03-01

    Ocean acidification (OA) and hypoxic events are increasing worldwide problems, their interactive effects have not been well clarified, although their co-occurrence is prevalent. The East China Sea (the Yangtze River estuary area) suffers from not only coastal hypoxia but also pH fluctuation, representing an ideal study site to explore the combined effect of OA and hypoxia on marine bivalves. We experimentally evaluated the antioxidant response of the mussel Mytilus coruscus exposed to three pH levels (8.1, 7.7 and 7.3) at two dissolved oxygen (DO) levels (2.0mgL -1 and 6.0mgL -1 ) for 72h. Activities of superoxide dismutase, catalase, glutathione peroxidase, acid phosphatase, and alkaline phosphatase and levels of malondialdehyde were measured in gills and hemolymph. All enzymatic activities in hemolymph and gills followed a similar pattern throughout the experiment duration. Generally, low DO showed greater effects on enzyme activities than elevated CO 2 . Significant interactions between DO, pH and time were only observed at superoxide dismutase and catalase in both tissues. PCA revealed positive relationships between most enzyme activities in both gills and hemolymph with the exception of alkaline phosphatase activity and the level of malondialdehyde in the hemolymph. Overall, our results suggested that decreased pH and low DO induced similar antioxidant responses in the hard shelled mussel, and showed an additive effect on most enzyme activities. The evaluation of multiple environmental stressors, a more realistic scenario than single ones, is crucial to predict the effect of future global changes on coastal species and our results supply some insights on the potential combined effects of reduced pH and DO on marine bivalves. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Development of QCD jets emitted by color-singlet sources

    International Nuclear Information System (INIS)

    Ellis, R.K.; Gunion, J.F.; Kalinowski, J.; Webber, B.R.

    1985-01-01

    We compare the angular-ordering approximation to QCD jet development with full calculations to order αsub(s) in the following cases: emission of quark jets by a color-singlet vector source (as in e + e - annihilation) and emission of gluon jets by a color-singlet scalar (Fsup(a)sub(μν)Fsup(aμν)) source. In contrast to the case of a color-octet (gluon) source, we find that the approximation is good in those regions of phase space where the next-to-leading corrections to the amplitude are large. (orig.)

  18. Combining tree-ring metal concentrations and lead, carbon and oxygen isotopes to reconstruct peri-urban atmospheric pollution

    Directory of Open Access Journals (Sweden)

    Annick Doucet

    2012-08-01

    Full Text Available In this study, we analysed the tree-ring metal concentrations and isotope ratios of five stands located in three contrasted settings to infer the diffuse air pollution history of the northern part of the Windsor–Québec City Corridor in eastern Canada. Tree-ring series show that the Cd and Zn accumulation rates were higher between 1960 and 1986 and that the long-term acidification of the soil (Ca/Al series was likely induced by NOx and SOx deposition (δ15N and δ13C trends as proxy. The Pb concentrations and 206Pb/207Pb ratios indicate that the dominant source of lead from 1880 to the 1920s was the combustion of north-eastern American coal, which was succeeded by the combustion of leaded gasoline from the 1920s to the end of the 1980s. Our modelling approach allows separating the climatic and anthropogenic effects on the tree-ring δ13C and δ18O responses. Diffuse air pollution caused an enrichment in 13C in all stands and a decrease of the δ18O values only in three of the stands. This study indicates that dendrogeochemistry can show contrasted responses to environmental changes and that the combination of several independent indicators constitutes a powerful tool to reconstruct the air pollution history in the complex context of peri-urban regions.

  19. Effect of oxygen vacancy and dopant concentration on the magnetic properties of high spin Co2+ doped TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Choudhury, B.; Choudhury, A.; Maidul Islam, A.K.M.; Alagarsamy, P.; Mukherjee, M.

    2011-01-01

    Co doped TiO 2 nanoparticles have been synthesized by a simple sol-gel route taking 7.5, 9.5 and 10.5 mol% of cobalt concentration. Formation of nanoparticles is confirmed by XRD and TEM. Increase in d-spacing occurs for (0 0 4) and (2 0 0) peak with increase in impurity content. Valence states of Co and its presence in the doped material is confirmed by XPS and EDX. The entire vacuum annealed samples show weak ferromagnetism. Increased magnetization is found for 9.5 mol% but this value again decreases for 10.5 mol% due to antiferromagnetic interactions. A blocking temperature of 37.9 K is obtained, which shows shifting to high temperature as the dopant concentration is increased. The air annealed sample shows only paramagnetic behavior. Temperature dependent magnetic measurements for the air annealed sample shows antiferromagnetic behavior with a Curie-Weiss temperature of -16 K. Here we report that oxygen vacancy and cobalt aggregates are a key factor for inducing ferromagnetism-superparamagnetism in the vacuum annealed sample. Appearance of negative Curie-Weiss temperature reveals the presence of antiferromagnetic Co 3 O 4 , which is the oxidation result of metallic Co or cobalt clusters present on the host TiO 2 . - Research highlights: → Oxygen vacancy induces ferromagnetism in cobalt doped anatase TiO2 nanoparticles. → On air annealing the sample loses ferromagnetism giving rise to paramagnetism. → Saturation magnetization decreases at higher doping concentration. → Blocking of magnetic moment occurs due to the presence of cobalt clusters.

  20. Different valence Sn doping - A simple way to detect oxygen concentration variation of ZnO quantum dots synthesized under ultrasonic irradiation.

    Science.gov (United States)

    Yang, Weimin; Zhang, Bing; Zhang, Qitu; Wang, Lixi; Song, Bo; Wu, Fan; Wong, C P

    2017-09-01

    An ultrasonic method is employed to synthesize the Sn doped Zn 0.95 Sn 0.05 O quantum dots with green light emission. Sn 2+ and Sn 4+ ions are used to create different optical defects inside Zn 0.95 Sn 0.05 O quantum dots and the changing trend of oxygen concentration under different ultrasonic irradiation power are investigated. The photoluminescence spectra are employed to characterize the optical defects of Zn 0.95 Sn 0.05 O quantum dots. The UV-vis spectra are used to study the band gap of Zn 0.95 Sn 0.05 O quantum dots, which is influenced by their sizes. The results indicate that ultrasonic power would influence the size of Zn 0.95 Sn 0.05 O quantum dots as well as the type and quantity of defects in ZnO quantum dots. Changing trends in size of Sn 2+ and Sn 4+ doped Zn 0.95 Sn 0.05 O quantum dots are quite similar with each other, while the changing trends in optical defects types and concentration of Sn 2+ and Sn 4+ doped Zn 0.95 Sn 0.05 O quantum dots are different. The difference of the optical defects concentration changing between Sn 2+ doped Zn 0.95 Sn 0.05 O quantum dots (V O defects) and Sn 4+ doped Zn 0.95 Sn 0.05 O quantum dots (O Zn and O i defects) shows that the formation process of ZnO under ultrasonic irradiation wiped oxygen out. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Atmospheric Oxygen Concentrations for the Past 350 Myr Modeled from the δ13C of C3 Land Plants

    Science.gov (United States)

    Nordt, L.; Breecker, D.

    2016-12-01

    Numerous studies have focused on the systematic collection of long-term d13C records from marine sediments, but no such isotopic compilation exists for C3 land plants. Consequently, we gathered a meta-data base of 8003 plant-derived δ13C values (ISOORG) from various carbon sources binned into 5 myr time steps. The results of this investigation were reported in a recent publication showing that most δ13C sources co-vary with ten CIEs during the last 400 myr. For this paper we culled ISOORG to produce ISOORG16-H that contains 7025 plant-derived δ13C values from paleo-moist environments to reflect secular controls on the δ13C of C3 plants. We then constructed atmospheric pO2 curves for the past 350 myr using prior experimental work showing a direct relationship between the Δ13C of C3 plants and pO2 concentration. Periods of hyperoxia (25-30% pO2) were identified from 300-250, 225-190, and 110-105 myr, and intervals of hypoxia (10-15% pO2) from 350-345, 245-230, and 185-115 myr. During the last 150 myr, pO2 stabilized at 17-24% except for a notable positive excursion from 110-105 myr. Hyperoxia, apparently from widespread carbon burial, supports the notion of insect gigantism during the Late Paleozoic. Hypoxia during the early Triassic correlates with the coal gap following the collapse of Paleozoic ecosystems. Rising pO2 in the late Triassic seems to reflect renewed carbon burial from reorganization of Mesozoic ecosystems. The middle Mesozoic is characterized by low pO2 during an intense greenhouse interval, with ambient conditions ensuing thereafter possibly linked to carbon burial from the radiation of angiosperms. pO2 concentrations >14% suggest wildfires persisted through the study interval except possibly at 160 and 140 myr. Intervals of low pO2 concentration were likely accompanied by lower atmospheric pressure and higher temperatures, particularly from 245-230 myr and 180-120 myr. Our O2 reconstructions conform with GEOCARBSULF, but not with proxy

  2. Effects of transient bottom water currents and oxygen concentrations on benthic exchange rates as assessed by eddy correlation measurements

    DEFF Research Database (Denmark)

    Holtappels, Moritz; Glud, Ronnie N.; Doris, Daphne

    2013-01-01

    Eddy correlation (EC) measurements in the benthic boundary layer (BBL) allow estimating benthic O2 uptake from a point distant to the sediment surface. This noninvasive approach has clear advantages as it does not disturb natural hydrodynamic conditions, integrates the flux over a large foot-print...... area and allows many repetitive flux measurements. A drawback is, however, that the measured flux in the bottom water is not necessarily equal to the flux across the sediment-water interface. A fundamental assumption of the EC technique is that mean current velocities and mean O2 concentrations...... in the bottom water are in steady state, which is seldom the case in highly dynamic environments like coastal waters. Therefore, it is of great importance to estimate the error introduced by nonsteady state conditions. We investigated two cases of transient conditions. First, the case of transient O2...

  3. Singlet Exciton Lifetimes in Conjugated Polymer Films for Organic Solar Cells

    KAUST Repository

    Dimitrov, Stoichko; Schroeder, Bob; Nielsen, Christian; Bronstein, Hugo; Fei, Zhuping; McCulloch, Iain; Heeney, Martin; Durrant, James

    2016-01-01

    The lifetime of singlet excitons in conjugated polymer films is a key factor taken into account during organic solar cell device optimization. It determines the singlet exciton diffusion lengths in polymer films and has a direct impact

  4. Robust singlet fission in pentacene thin films with tuned charge transfer interactions.

    Science.gov (United States)

    Broch, K; Dieterle, J; Branchi, F; Hestand, N J; Olivier, Y; Tamura, H; Cruz, C; Nichols, V M; Hinderhofer, A; Beljonne, D; Spano, F C; Cerullo, G; Bardeen, C J; Schreiber, F

    2018-03-05

    Singlet fission, the spin-allowed photophysical process converting an excited singlet state into two triplet states, has attracted significant attention for device applications. Research so far has focused mainly on the understanding of singlet fission in pure materials, yet blends offer the promise of a controlled tuning of intermolecular interactions, impacting singlet fission efficiencies. Here we report a study of singlet fission in mixtures of pentacene with weakly interacting spacer molecules. Comparison of experimentally determined stationary optical properties and theoretical calculations indicates a reduction of charge-transfer interactions between pentacene molecules with increasing spacer molecule fraction. Theory predicts that the reduced interactions slow down singlet fission in these blends, but surprisingly we find that singlet fission occurs on a timescale comparable to that in pure crystalline pentacene. We explain the observed robustness of singlet fission in such mixed films by a mechanism of exciton diffusion to hot spots with closer intermolecular spacings.

  5. Effect of low-oxygen-concentration layer on iron gettering capability of carbon-cluster ion-implanted Si wafer for CMOS image sensors

    Science.gov (United States)

    Onaka-Masada, Ayumi; Nakai, Toshiro; Okuyama, Ryosuke; Okuda, Hidehiko; Kadono, Takeshi; Hirose, Ryo; Koga, Yoshihiro; Kurita, Kazunari; Sueoka, Koji

    2018-02-01

    The effect of oxygen (O) concentration on the Fe gettering capability in a carbon-cluster (C3H5) ion-implanted region was investigated by comparing a Czochralski (CZ)-grown silicon substrate and an epitaxial growth layer. A high Fe gettering efficiency in a carbon-cluster ion-implanted epitaxial growth layer, which has a low oxygen region, was observed by deep-level transient spectroscopy (DLTS) and secondary ion mass spectroscopy (SIMS). It was demonstrated that the amount of gettered Fe in the epitaxial growth layer is approximately two times higher than that in the CZ-grown silicon substrate. Furthermore, by measuring the cathodeluminescence, the number of intrinsic point defects induced by carbon-cluster ion implantation was found to differ between the CZ-grown silicon substrate and the epitaxial growth layer. It is suggested that Fe gettering by carbon-cluster ion implantation comes through point defect clusters, and that O in the carbon-cluster ion-implanted region affects the formation of gettering sinks for Fe.

  6. Enhanced cycling performance of a Li metal anode in a dimethylsulfoxide-based electrolyte using highly concentrated lithium salt for a lithium-oxygen battery

    Science.gov (United States)

    Togasaki, Norihiro; Momma, Toshiyuki; Osaka, Tetsuya

    2016-03-01

    Stable charge-discharge cycling behavior for a lithium metal anode in a dimethylsulfoxide (DMSO)-based electrolyte is strongly desired of lithium-oxygen batteries, because the Li anode is rapidly exhausted as a result of side reactions during cycling in the DMSO solution. Herein, we report a novel electrolyte design for enhancing the cycling performance of Li anodes by using a highly concentrated DMSO-based electrolyte with a specific Li salt. Lithium nitrate (LiNO3), which forms an inorganic compound (Li2O) instead of a soluble product (Li2S) on a lithium surface, exhibits a >20% higher coulombic efficiency than lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium perchlorate, regardless of the loading current density. Moreover, the stable cycling of Li anodes in DMSO-based electrolytes depends critically on the salt concentration. The highly concentrated electrolyte 4.0 M LiNO3/DMSO displays enhanced and stable cycling performance comparable to that of carbonate-based electrolytes, which had not previously been achieved. We suppose this enhancement is due to the absence of free DMSO solvent in the electrolyte and the promotion of the desolvation of Li ions on the solid electrolyte interphase surface, both being consequences of the unique structure of the electrolyte.

  7. High oxygen partial pressure increases photodynamic effect on HeLa cell lines in the presence of chloraluminium phthalocyanine.

    Science.gov (United States)

    Bajgar, Robert; Kolarova, Hana; Bolek, Lukas; Binder, Svatopluk; Pizova, Klara; Hanakova, Adela

    2014-08-01

    Photodynamic therapy (PDT) is linked with oxidative damage of biomolecules causing significant impairment of essential cellular functions that lead to cell death. It is the reason why photodynamic therapy has found application in treatment of different oncological, cardiovascular, skin and eye diseases. Efficacy of PDT depends on combined action of three components; sensitizer, light and oxygen. In the present study, we examined whether higher partial pressure of oxygen increases lethality in HeLa cell lines exposed to light in the presence of chloraluminium phthalocyanine disulfonate (ClAlPcS2). ClAlPcS2- sensitized HeLa cells incubated under different oxygen conditions were exposed to PDT. Production of singlet oxygen ((1)O2) and other forms of reactive oxygen species (ROS) as well as changes in mitochondrial membrane potential were determined by appropriately sensitive fluorescence probes. The effect of PDT on HeLa cell viability under different oxygen conditions was quantified using the standard methylthiazol tetrazolium (MTT) test. At the highest oxygen concentration of 28 ± 2 mg/l HeLa cells were significantly more sensitive to light-activated ClAlPcS2 (EC50=0.29 ± 0.05 μM) in comparison to cells incubated at lower oxygen concentrations of 8 ± 0.5 and 0.5 ± 0.1 mg/l, where the half maximal effective concentration was 0.42 ± 0.06 μM and 0.94 ± 0.14 μM, respectively. Moreover, we found that the higher presence of oxygen is accompanied with higher production of singlet oxygen, a higher rate of type II photodynamic reactions, and a significant drop in the mitochondrial membrane potential. These results demonstrate that the photodynamic effect in cervical cancer cells utilizing ClAlPcS2 significantly depends on oxygen level. Copyright© 2014 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  8. First-Principle Characterization for Singlet Fission Couplings.

    Science.gov (United States)

    Yang, Chou-Hsun; Hsu, Chao-Ping

    2015-05-21

    The electronic coupling for singlet fission, an important parameter for determining the rate, has been found to be too small unless charge-transfer (CT) components were introduced in the diabatic states, mostly through perturbation or a model Hamiltonian. In the present work, the fragment spin difference (FSD) scheme was generalized to calculate the singlet fission coupling. The largest coupling strength obtained was 14.8 meV for two pentacenes in a crystal structure, or 33.7 meV for a transition-state structure, which yielded a singlet fission lifetime of 239 or 37 fs, generally consistent with experimental results (80 fs). Test results with other polyacene molecules are similar. We found that the charge on one fragment in the S1 diabatic state correlates well with FSD coupling, indicating the importance of the CT component. The FSD approach is a useful first-principle method for singlet fission coupling, without the need to include the CT component explicitly.

  9. 1,3-Diphenylisobenzofuran: a Model Chromophore for Singlet Fission

    Czech Academy of Sciences Publication Activity Database

    Johnson, J. C.; Michl, Josef

    2017-01-01

    Roč. 375, č. 5 (2017), č. článku 80. ISSN 2365-0869 R&D Projects: GA ČR GA15-19143S Institutional support: RVO:61388963 Keywords : 1,3-diphenylisobenzofuran * photophysics * solar energy * singlet fission * covalent dimers Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 4.033, year: 2016

  10. Status of the scalar singlet dark matter model

    Energy Technology Data Exchange (ETDEWEB)

    Athron, Peter; Balazs, Csaba [Monash University, School of Physics and Astronomy, Melbourne, VIC (Australia); Australian Research Council Centre of Excellence for Particle Physics at the Tera-scale (Australia); Bringmann, Torsten; Dal, Lars A.; Krislock, Abram; Raklev, Are [University of Oslo, Department of Physics, Oslo (Norway); Buckley, Andy [University of Glasgow, SUPA, School of Physics and Astronomy, Glasgow (United Kingdom); Chrzaszcz, Marcin [Universitaet Zuerich, Physik-Institut, Zurich (Switzerland); Polish Academy of Sciences, H. Niewodniczanski Institute of Nuclear Physics, Krakow (Poland); Conrad, Jan; Edsjoe, Joakim; Farmer, Ben [AlbaNova University Centre, Oskar Klein Centre for Cosmoparticle Physics, Stockholm (Sweden); Stockholm University, Department of Physics, Stockholm (Sweden); Cornell, Jonathan M. [McGill University, Department of Physics, Montreal, QC (Canada); Jackson, Paul; White, Martin [Australian Research Council Centre of Excellence for Particle Physics at the Tera-scale (Australia); University of Adelaide, Department of Physics, Adelaide, SA (Australia); Kahlhoefer, Felix [DESY, Hamburg (Germany); Kvellestad, Anders; Savage, Christopher [NORDITA, Stockholm (Sweden); McKay, James; Scott, Pat [Imperial College London, Department of Physics, Blackett Laboratory, London (United Kingdom); Mahmoudi, Farvah [Univ. Lyon, Univ. Lyon 1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, Saint-Genis-Laval (France); CERN, Theoretical Physics Department, Geneva (Switzerland); Martinez, Gregory D. [University of California, Physics and Astronomy Department, Los Angeles, CA (United States); Putze, Antje [LAPTh, Universite de Savoie, CNRS, Annecy-le-Vieux (France); Rogan, Christopher [Harvard University, Department of Physics, Cambridge, MA (United States); Saavedra, Aldo [Australian Research Council Centre of Excellence for Particle Physics at the Tera-scale (Australia); The University of Sydney, Centre for Translational Data Science, Faculty of Engineering and Information Technologies, School of Physics, Sydney, NSW (Australia); Serra, Nicola [Universitaet Zuerich, Physik-Institut, Zurich (Switzerland); Weniger, Christoph [University of Amsterdam, GRAPPA, Institute of Physics, Amsterdam (Netherlands); Collaboration: The GAMBIT Collaboration

    2017-08-15

    One of the simplest viable models for dark matter is an additional neutral scalar, stabilised by a Z{sub 2} symmetry. Using the GAMBIT package and combining results from four independent samplers, we present Bayesian and frequentist global fits of this model. We vary the singlet mass and coupling along with 13 nuisance parameters, including nuclear uncertainties relevant for direct detection, the local dark matter density, and selected quark masses and couplings. We include the dark matter relic density measured by Planck, direct searches with LUX, PandaX, SuperCDMS and XENON100, limits on invisible Higgs decays from the Large Hadron Collider, searches for high-energy neutrinos from dark matter annihilation in the Sun with IceCube, and searches for gamma rays from annihilation in dwarf galaxies with the Fermi-LAT. Viable solutions remain at couplings of order unity, for singlet masses between the Higgs mass and about 300 GeV, and at masses above ∝ 1 TeV. Only in the latter case can the scalar singlet constitute all of dark matter. Frequentist analysis shows that the low-mass resonance region, where the singlet is about half the mass of the Higgs, can also account for all of dark matter, and remains viable. However, Bayesian considerations show this region to be rather fine-tuned. (orig.)

  11. Generation of deviation parameters for amino acid singlets, doublets ...

    Indian Academy of Sciences (India)

    We present a new method, secondary structure prediction by deviation parameter (SSPDP) for predicting the secondary structure of proteins from amino acid sequence. Deviation parameters (DP) for amino acid singlets, doublets and triplets were computed with respect to secondary structural elements of proteins based on ...

  12. Flavor-singlet spectrum in multi-flavor QCD

    Science.gov (United States)

    Aoki, Yasumichi; Aoyama, Tatsumi; Bennett, Ed; Kurachi, Masafumi; Maskawa, Toshihide; Miura, Kohtaroh; Nagai, Kei-ichi; Ohki, Hiroshi; Rinaldi, Enrico; Shibata, Akihiro; Yamawaki, Koichi; Yamazaki, Takeshi

    2018-03-01

    Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.

  13. Flavor-singlet spectrum in multi-flavor QCD

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, Yasamichi; Rinaldi, Enrico

    2017-06-18

    Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.

  14. Status of the scalar singlet dark matter model

    Science.gov (United States)

    Athron, Peter; Balázs, Csaba; Bringmann, Torsten; Buckley, Andy; Chrząszcz, Marcin; Conrad, Jan; Cornell, Jonathan M.; Dal, Lars A.; Edsjö, Joakim; Farmer, Ben; Jackson, Paul; Kahlhoefer, Felix; Krislock, Abram; Kvellestad, Anders; McKay, James; Mahmoudi, Farvah; Martinez, Gregory D.; Putze, Antje; Raklev, Are; Rogan, Christopher; Saavedra, Aldo; Savage, Christopher; Scott, Pat; Serra, Nicola; Weniger, Christoph; White, Martin

    2017-08-01

    One of the simplest viable models for dark matter is an additional neutral scalar, stabilised by a Z_2 symmetry. Using the GAMBIT package and combining results from four independent samplers, we present Bayesian and frequentist global fits of this model. We vary the singlet mass and coupling along with 13 nuisance parameters, including nuclear uncertainties relevant for direct detection, the local dark matter density, and selected quark masses and couplings. We include the dark matter relic density measured by Planck, direct searches with LUX, PandaX, SuperCDMS and XENON100, limits on invisible Higgs decays from the Large Hadron Collider, searches for high-energy neutrinos from dark matter annihilation in the Sun with IceCube, and searches for gamma rays from annihilation in dwarf galaxies with the Fermi-LAT. Viable solutions remain at couplings of order unity, for singlet masses between the Higgs mass and about 300 GeV, and at masses above ˜ 1 TeV. Only in the latter case can the scalar singlet constitute all of dark matter. Frequentist analysis shows that the low-mass resonance region, where the singlet is about half the mass of the Higgs, can also account for all of dark matter, and remains viable. However, Bayesian considerations show this region to be rather fine-tuned.

  15. Inhibitory effects of ZnO nanoparticles on aerobic wastewater biofilms from oxygen concentration profiles determined by microelectrodes

    International Nuclear Information System (INIS)

    Hou, Jun; Miao, Lingzhan; Wang, Chao; Wang, Peifang; Ao, Yanhui; Qian, Jin; Dai, Shanshan

    2014-01-01

    Highlights: • Temporal and spatial inhibitory effects of ZnO NPs on biofilms were investigated. • 50 mg/L nano-ZnO inhibited the microbial activities only in biofilm outer layer. • Adsorbed ZnO NPs had no adverse effects on the cell membrane integrity of biofilms. • Dissolution of ZnO NPs to toxic zinc ions was the main mechanism of toxicity. - Abstract: The presence of ZnO NPs in waste streams can negatively affect the efficiency of biological nutrient removal from wastewater. However, details of the toxic effects of ZnO NPs on microbial activities of wastewater biofilms have not yet been reported. In this study, the temporal and spatial inhibitory effects of ZnO NPs on the O 2 respiration activities of aerobic wastewater biofilms were investigated using an O 2 microelectrode. The resulting time–course microelectrode measurements demonstrated that ZnO NPs inhibited O 2 respiration within 2 h. The spatial distributions of net specific O 2 respiration were determined in biofilms with and without treatment of 5 or 50 mg/L ZnO NPs. The results showed that 50 mg/L of nano-ZnO inhibited the microbial activities only in the outer layer (∼200 μm) of the biofilms, and bacteria present in the deeper parts of the biofilms became even more active. Scanning electron microscopy (SEM) analysis showed that the ZnO NPs were adsorbed onto the biofilm, but these NPs had no adverse effects on the cell membrane integrity of the biofilms. It was found that the inhibition of O 2 respiration induced by higher concentrations of ZnO NPs (50 mg/L) was mainly due to the release of zinc ions by dissolution of the ZnO NPs

  16. Inhibitory effects of ZnO nanoparticles on aerobic wastewater biofilms from oxygen concentration profiles determined by microelectrodes

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Jun [Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098 (China); College of Environment, Hohai University, Nanjing 210098 (China); Miao, Lingzhan, E-mail: mlz1988@126.com [Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098 (China); College of Environment, Hohai University, Nanjing 210098 (China); Wang, Chao, E-mail: hhuhjy973@126.com [Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098 (China); College of Environment, Hohai University, Nanjing 210098 (China); Wang, Peifang; Ao, Yanhui; Qian, Jin; Dai, Shanshan [Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098 (China); College of Environment, Hohai University, Nanjing 210098 (China)

    2014-07-15

    Highlights: • Temporal and spatial inhibitory effects of ZnO NPs on biofilms were investigated. • 50 mg/L nano-ZnO inhibited the microbial activities only in biofilm outer layer. • Adsorbed ZnO NPs had no adverse effects on the cell membrane integrity of biofilms. • Dissolution of ZnO NPs to toxic zinc ions was the main mechanism of toxicity. - Abstract: The presence of ZnO NPs in waste streams can negatively affect the efficiency of biological nutrient removal from wastewater. However, details of the toxic effects of ZnO NPs on microbial activities of wastewater biofilms have not yet been reported. In this study, the temporal and spatial inhibitory effects of ZnO NPs on the O{sub 2} respiration activities of aerobic wastewater biofilms were investigated using an O{sub 2} microelectrode. The resulting time–course microelectrode measurements demonstrated that ZnO NPs inhibited O{sub 2} respiration within 2 h. The spatial distributions of net specific O{sub 2} respiration were determined in biofilms with and without treatment of 5 or 50 mg/L ZnO NPs. The results showed that 50 mg/L of nano-ZnO inhibited the microbial activities only in the outer layer (∼200 μm) of the biofilms, and bacteria present in the deeper parts of the biofilms became even more active. Scanning electron microscopy (SEM) analysis showed that the ZnO NPs were adsorbed onto the biofilm, but these NPs had no adverse effects on the cell membrane integrity of the biofilms. It was found that the inhibition of O{sub 2} respiration induced by higher concentrations of ZnO NPs (50 mg/L) was mainly due to the release of zinc ions by dissolution of the ZnO NPs.

  17. Mechanistic and Kinetic Study of Singlet O2 Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry.

    Science.gov (United States)

    Liu, Fangwei; Lu, Wenchao; Yin, Xunlong; Liu, Jianbo

    2016-01-01

    We report a reaction apparatus developed to monitor singlet oxygen ((1)O2) reactions in solution using on-line ESI mass spectrometry and spectroscopy measurements. (1)O2 was generated in the gas phase by the reaction of H2O2 with Cl2, detected by its emission at 1270 nm, and bubbled into aqueous solution continuously. (1)O2 concentrations in solution were linearly related to the emission intensities of airborne (1)O2, and their absolute scales were established based on a calibration using 9,10-anthracene dipropionate dianion as an (1)O2 trapping agent. Products from (1)O2 oxidation were monitored by UV-Vis absorption and positive/negative ESI mass spectra, and product structures were elucidated using collision-induced dissociation-tandem mass spectrometry. To suppress electrical discharge in negative ESI of aqueous solution, methanol was added to electrospray via in-spray solution mixing using theta-glass ESI emitters. Capitalizing on this apparatus, the reaction of (1)O2 with methionine was investigated. We have identified methionine oxidation intermediates and products at different pH, and measured reaction rate constants. (1)O2 oxidation of methionine is mediated by persulfoxide in both acidic and basic solutions. Persulfoxide continues to react with another methionine, yielding methionine sulfoxide as end-product albeit with a much lower reaction rate in basic solution. Density functional theory was used to explore reaction potential energy surfaces and establish kinetic models, with solvation effects simulated using the polarized continuum model. Combined with our previous study of gas-phase methionine ions with (1)O2, evolution of methionine oxidation pathways at different ionization states and in different media is described.

  18. Sea quark matrix elements and flavor singlet spectroscopy on the lattice

    International Nuclear Information System (INIS)

    Lagae, J.F.

    1996-01-01

    I summarize the results of three recent lattice studies which use stochastic estimator techniques in order to investigate the flavor singlet dynamics in QCD. These include a measurement of the pion-nucleon σ-term, the computation of the flavor singlet axial coupling constant of the nucleon and a determination of flavor singlet meson screening lengths in finite temperature QCD

  19. Achieving low effluent NO3-N and TN concentrations in low influent chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio without using external carbon source

    Science.gov (United States)

    Cao, Jiashun; Oleyiblo, Oloche James; Xue, Zhaoxia; Otache, Y. Martins; Feng, Qian

    2015-07-01

    Two mathematical models were used to optimize the performance of a full-scale biological nutrient removal (BNR) activated treatment plant, a plug-flow bioreactors operated in a 3-stage phoredox process configuration, anaerobic anoxic oxic (A2/O). The ASM2d implemented on the platform of WEST2011 software and the BioWin activated sludge/anaerobic digestion (AS/AD) models were used in this study with the aim of consistently achieving the designed effluent criteria at a low operational cost. Four ASM2d parameters (the reduction factor for denitrification , the maximum growth rate of heterotrophs (µH), the rate constant for stored polyphosphates in PAOs ( q pp), and the hydrolysis rate constant ( k h)) were adjusted. Whereas three BioWin parameters (aerobic decay rate ( b H), heterotrophic dissolved oxygen (DO) half saturation ( K OA), and Y P/acetic) were adjusted. Calibration of the two models was successful; both models have average relative deviations (ARD) less than 10% for all the output variables. Low effluent concentrations of nitrate nitrogen (N-NO3), total nitrogen (TN), and total phosphorus (TP) were achieved in a full-scale BNR treatment plant having low influent chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio (COD/TKN). The effluent total nitrogen and nitrate nitrogen concentrations were improved by 50% and energy consumption was reduced by approximately 25%, which was accomplished by converting the two-pass aerobic compartment of the plug-flow bioreactor to anoxic reactors and being operated in an alternating mode. Findings in this work are helpful in improving the operation of wastewater treatment plant while eliminating the cost of external carbon source and reducing energy consumption.

  20. Singlet exciton fission in polycrystalline pentacene: from photophysics toward devices.

    Science.gov (United States)

    Wilson, Mark W B; Rao, Akshay; Ehrler, Bruno; Friend, Richard H

    2013-06-18

    Singlet exciton fission is the process in conjugated organic molecules bywhich a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers first reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These investigations used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest has been recently rekindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating additional photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chemistry, and small-molecule device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycrystalline thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, we review the results of our recent transient absorption and device-based studies of polycrystalline pentacene. We address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins our conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, we discuss our demonstration that triplet excitons

  1. Effects of Intermolecular Coupling on Excimer Formation and Singlet Fission

    Science.gov (United States)

    Mauck, Catherine McKay

    The development of organic photovoltaic devices benefits from understanding the fundamental processes underlying charge generation in thin films of organic semiconductors. This dissertation exploits model systems of pi-stacked chromophores such as perylene-3,4:9,10-bis(dicarboximide) (PDI) and 3,6-bis(aryl)diketopyrrolopyrrole (DPP) to study these processes using ultrafast electronic and vibrational spectroscopy. In particular, the characterization of covalent molecular dimers, thin films, and solution aggregates can reveal how supramolecular order affects photophysical properties. PDI and DPP are organic semiconductors that have been widely studied in organic photovoltaics, due to their strong visible absorption and excellent chemical stability. As solution-phase monomers, they are highly fluorescent, but in the thin film environment of photovoltaic devices these planar aromatic molecules couple to one another, stacking largely through pi-pi interactions. In self-assembled stacks of PDI, strong interchromophore coupling may disrupt charge separation through the formation of excimer states, preventing the generation of free carriers. By studying molecular dimers of PDI with different pi-stacked geometry, femtosecond visible pump mid-infrared probe spectroscopy allows direct observation of the structural dynamics associated with excimer state relaxation, showing that this low-energy state is primarily coupled to the core modes that shift as planarization and rotation lead to the most stable excimer geometry. PDI is also able to undergo singlet fission in thin films and aggregates. Singlet fission is the process in which a singlet excited state is downconverted into two triplet excitons, when the energy of its first singlet excited state is at least twice the energy of the lowest triplet state in an appropriately coupled molecular system. This spin-allowed, ultrafast process enables a theoretical yield of two charge carriers per incident photon, making it a

  2. Oxygen vacancies enabled enhancement of catalytic property of Al reduced anatase TiO{sub 2} in the decomposition of high concentration ozone

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Yanhua; Zhang, Xiaolei [Shanghai Institute of Technology, Shanghai 200235 (China); Chen, Li [East China Normal University, Shanghai 200062 (China); Wang, Xiaorui [Shanghai Institute of Technology, Shanghai 200235 (China); Zhang, Na, E-mail: nzhang@sit.edu.cn [Shanghai Institute of Technology, Shanghai 200235 (China); Liu, Yufeng [Shanghai Institute of Technology, Shanghai 200235 (China); Fang, Yongzheng, E-mail: fyz1003@sina.com [Shanghai Institute of Technology, Shanghai 200235 (China)

    2017-06-15

    The catalytic decomposition of gaseous ozone (O{sub 3}) is investigated using anatase TiO{sub 2} (A-TiO{sub 2}) and Aluminum-reduced A-TiO{sub 2} (ARA-TiO{sub 2}) at high concentration and high relative humidity (RH) without light illumination. Compared with the pristine A-TiO{sub 2}, the ARA-TiO{sub 2} sample possesses a unique crystalline core-amorphous shell structure. It is proved to be an excellent solar energy “capture” for solar thermal collectors due to lots of oxygen vacancies. The results indicate that the overall decomposition efficiency of O{sub 3} without any light irradiation has been greatly improved from 4.8% on A-TiO{sub 2} to 100% on ARA-TiO{sub 2} under the RH=100% condition. The ozone conversion over T500/ARA-TiO{sub 2} catalyst is still maintained at 95% after a 72 h test under the reaction condition of 18.5 g/m{sup 3} ozone initial concentration, and RH=90%. The results can be explained that T500/ARA-TiO{sub 2} possesses the largest amorphous contour, the lowest crystallinity, the most surface-active Ti{sup 3+}/T{sup i4+}couples, and the most oxygen vacancies. This result opens a new door to widen the application of TiO{sub 2} in the thermal-catalytic field. - Graphical abstract: The anatase-TiO{sub 2} with various oxidation states and oxygen vacancies have been obtained by aluminum-reduction, and the decomposition efficiency of O{sub 3} has been greatly improved from 4.8% to 100% without irradiation under the RH=100% condition. - Highlights: • The decomposition of gaseous ozone over Al reduced TiO2 (ARA-TiO{sub 2}) is firstly reported. • The decomposition efficiency is up to 100% without any light irradiation on ARA-TiO{sub 2} under RH=100% condition. • The ozone conversion is maintained at 95% after a 72 h test, when C{sub inlet}=18.5 g/m{sup 3} and RH=90%.

  3. Influence of Oxygen Concentration on the Performance of Ultra-Thin RF Magnetron Sputter Deposited Indium Tin Oxide Films as a Top Electrode for Photovoltaic Devices

    Directory of Open Access Journals (Sweden)

    Jephias Gwamuri

    2016-01-01

    Full Text Available The opportunity for substantial efficiency enhancements of thin film hydrogenated amorphous silicon (a-Si:H solar photovoltaic (PV cells using plasmonic absorbers requires ultra-thin transparent conducting oxide top electrodes with low resistivity and high transmittances in the visible range of the electromagnetic spectrum. Fabricating ultra-thin indium tin oxide (ITO films (sub-50 nm using conventional methods has presented a number of challenges; however, a novel method involving chemical shaving of thicker (greater than 80 nm RF sputter deposited high-quality ITO films has been demonstrated. This study investigates the effect of oxygen concentration on the etch rates of RF sputter deposited ITO films to provide a detailed understanding of the interaction of all critical experimental parameters to help create even thinner layers to allow for more finely tune plasmonic resonances. ITO films were deposited on silicon substrates with a 98-nm, thermally grown oxide using RF magnetron sputtering with oxygen concentrations of 0, 0.4 and 1.0 sccm and annealed at 300 °C air ambient. Then the films were etched using a combination of water and hydrochloric and nitric acids for 1, 3, 5 and 8 min at room temperature. In-between each etching process cycle, the films were characterized by X-ray diffraction, atomic force microscopy, Raman Spectroscopy, 4-point probe (electrical conductivity, and variable angle spectroscopic ellipsometry. All the films were polycrystalline in nature and highly oriented along the (222 reflection. Ultra-thin ITO films with record low resistivity values (as low as 5.83 × 10−4 Ω·cm were obtained and high optical transparency is exhibited in the 300–1000 nm wavelength region for all the ITO films. The etch rate, preferred crystal lattice growth plane, d-spacing and lattice distortion were also observed to be highly dependent on the nature of growth environment for RF sputter deposited ITO films. The structural, electrical

  4. Accuracy of different sensors for the estimation of pollutant concentrations (total suspended solids, total and dissolved chemical oxygen demand) in wastewater and stormwater.

    Science.gov (United States)

    Lepot, Mathieu; Aubin, Jean-Baptiste; Bertrand-Krajewski, Jean-Luc

    2013-01-01

    Many field investigations have used continuous sensors (turbidimeters and/or ultraviolet (UV)-visible spectrophotometers) to estimate with a short time step pollutant concentrations in sewer systems. Few, if any, publications compare the performance of various sensors for the same set of samples. Different surrogate sensors (turbidity sensors, UV-visible spectrophotometer, pH meter, conductivity meter and microwave sensor) were tested to link concentrations of total suspended solids (TSS), total and dissolved chemical oxygen demand (COD), and sensors' outputs. In the combined sewer at the inlet of a wastewater treatment plant, 94 samples were collected during dry weather, 44 samples were collected during wet weather, and 165 samples were collected under both dry and wet weather conditions. From these samples, triplicate standard laboratory analyses were performed and corresponding sensors outputs were recorded. Two outlier detection methods were developed, based, respectively, on the Mahalanobis and Euclidean distances. Several hundred regression models were tested, and the best ones (according to the root mean square error criterion) are presented in order of decreasing performance. No sensor appears as the best one for all three investigated pollutants.

  5. Concentration-dependent induction of reactive oxygen species, cell cycle arrest and apoptosis in human liver cells after nickel nanoparticles exposure.

    Science.gov (United States)

    Ahmad, Javed; Alhadlaq, Hisham A; Siddiqui, Maqsood A; Saquib, Quaiser; Al-Khedhairy, Abdulaziz A; Musarrat, Javed; Ahamed, Maqusood

    2015-02-01

    Due to advent of nanotechnology, nickel nanoparticles (Ni NPs) are increasingly recognized for their utility in various applications including catalysts, sensors and electronics. However, the environmental and human health effects of Ni NPs have not been fully investigated. In this study, we examined toxic effects of Ni NPs in human liver (HepG2) cells. Ni NPs were prepared and characterized by X-ray diffraction, transmission electron microscopy and dynamic light scattering. We observed that Ni NPs (size, ∼28 nm; concentration range, 25-100 μg/mL) induced cytotoxicity in HepG2 cells and degree of induction was concentration-dependent. Ni NPs were also found to induce oxidative stress in dose-dependent manner evident by induction of reactive oxygen species and depletion of glutathione. Cell cycle analysis of cells treated with Ni NPs exhibited significant increase of apoptotic cell population in subG1 phase. Ni NPs also induced caspase-3 enzyme activity and apoptotic DNA fragmentation. Upregulation of cell cycle checkpoint gene p53 and bax/bcl-2 ratio with a concomitant loss in mitochondrial membrane potential suggested that Ni NPs induced apoptosis in HepG2 cells was mediated through mitochondrial pathway. This study warrants that applications of Ni NPs should be carefully assessed as to their toxicity to human health. © 2013 Wiley Periodicals, Inc.

  6. Lithium-Oxygen Batteries: At a Crossroads?

    DEFF Research Database (Denmark)

    Vegge, Tejs; García Lastra, Juan Maria; Siegel, Donald Jason

    2017-01-01

    In this current opinion, we critically review and discuss some of the most important recent findings in the field of rechargeable lithium-oxygen batteries. We discuss recent discoveries like the evolution of reactive singlet oxygen and the use of organic additives to bypass reactive LiO2 reaction...... intermediates, and their possible implications on the potential for commercialization of lithium-oxygen batteries. Finally, we perform a critical assessment of lithium-superoxide batteries and the reversibility of lithium-hydroxide batteries....

  7. Prevention of alloimmunization by ultraviolet-B irradiation. Inactivation of leukocytes and the generation of active oxygen and radicals

    International Nuclear Information System (INIS)

    Takahashi, Tsuneo; Mogi, Yuko; Sekiguchi, Sadayoshi; Akasaka, Junichi; Kamo, Naoki; Kuwabara, Mikinori.

    1994-01-01

    UV-B irradiation of platelet concentrates (PC) has been tried in several institutes to inactivate leukocytes in PC and prevent alloimmunization on platelet transfusion. However, the mechanism of inactivation of leukocytes contaminating PC has not been fully understood. It is known that UV-B light is absorbed by photosensitizers in cells and produces active oxygen and radicals, such as singlet oxygen, superioxide anions and hydroxyl radicals. These active oxygen or radicals should injure cellular components and this could cause the suppression of cellular functions. In this study, we investigated the relationships among UV-B irradiation, free radical generation and leukocyte inactivation. We found the evidence that active oxygen and radicals were produced in peripheral blood mononuclear cells by UV-B irradiation. UV-B irradiation suppressed the stimulatory function of leukocytes in a mixed lymphocyte reaction (MLR), and the suppression depended on the dosage of UV-B. Even a low dosage of UV-B, 10 J/m 2 , could inhibit the MLR if the irradiated cells were incubated at 37degC for 24 hours before co-culture with responder cells. Treatments of cells with the exogenous singlet oxygen or superoxide anions also caused suppression of the stimulatory function in the MLR, inhibition of capping formation of HLA-DR antigens, and an increase of intracellular free Ca 2+ levels as did the UV-B treatment. These results indicate that the active oxygen or radicals generated in UV-B-irradiated leukocytes could be one of the causes of leukocyte inactivation. (author0

  8. Effect of low oxygen concentrations on growth and alpha-amylase production of Aspergillus oryzae in model solid-state fermentation systems

    NARCIS (Netherlands)

    Rahardjo, Y.S.P.; Sie, S.; Weber, F.J.; Tramper, J.; Rinzema, A.

    2005-01-01

    Oxygen transfer in the fungal mat is a major concern in solid-state fermentation (SSF). Oxygen supply into the mycelial layers is hampered by diffusion limitation. For aerobic fungi, like Aspergillus oryzae, this oxygen depletion can be a severely limiting factor for growth and metabolite

  9. Effect of therapeutic plasma concentrations of non-steroidal anti-inflammatory drugs on the production of reactive oxygen species by activated rat neutrophils

    Directory of Open Access Journals (Sweden)

    Paino I.M.M.

    2005-01-01

    Full Text Available The release of reactive oxygen specie (ROS by activated neutrophil is involved in both the antimicrobial and deleterious effects in chronic inflammation. The objective of the present investigation was to determine the effect of therapeutic plasma concentrations of non-steroidal anti-inflammatory drugs (NSAIDs on the production of ROS by stimulated rat neutrophils. Diclofenac (3.6 µM, indomethacin (12 µM, naproxen (160 µM, piroxicam (13 µM, and tenoxicam (30 µM were incubated at 37ºC in PBS (10 mM, pH 7.4, for 30 min with rat neutrophils (1 x 10(6 cells/ml stimulated by phorbol-12-myristate-13-acetate (100 nM. The ROS production was measured by luminol and lucigenin-dependent chemiluminescence. Except for naproxen, NSAIDs reduced ROS production: 58 ± 2% diclofenac, 90 ± 2% indomethacin, 33 ± 3% piroxicam, and 45 ± 6% tenoxicam (N = 6. For the lucigenin assay, naproxen, piroxicam and tenoxicam were ineffective. For indomethacin the inhibition was 52 ± 5% and diclofenac showed amplification in the light emission of 181 ± 60% (N = 6. Using the myeloperoxidase (MPO/H2O2/luminol system, the effects of NSAIDs on MPO activity were also screened. We found that NSAIDs inhibited both the peroxidation and chlorinating activity of MPO as follows: diclofenac (36 ± 10, 45 ± 3%, indomethacin (97 ± 2, 100 ± 1%, naproxen (56 ± 8, 76 ± 3%, piroxicam (77 ± 5, 99 ± 1%, and tenoxicam (90 ± 2, 100 ± 1%, respectively (N = 3. These results show that therapeutic levels of NSAIDs are able to suppress the oxygen-dependent antimicrobial or oxidative functions of neutrophils by inhibiting the generation of hypochlorous acid.

  10. Effect of long-ter